If you need a temporary center channel, use any old cheap thing for now.
Basically you can either repair or replace your center channel.
Option
#1 : Use a similar speaker as your center speaker
You might be able to find a speaker that sounds similar to the rest of your system. Use a similar model from the same manufacturer and line if possible.
You can replace your center speaker with a bookshelf speaker and it might even sound better without the horizontal combing and lobing of a horizontal MTM/WTW etc. center. If the drivers are aligned vertically when installed in your setup, the dispersion will be symmetric. If the drivers are aligned horizontally, the bass and treble will diverge horizontally but it is not such a big issue IMO. It is also possible to use 2 bookshelf speakers wired together (to maintain symmetry) but I do not recommend it. If you do, abut the cabinets with the tweeters adjacent to each other.
You should be able to match the sonic quality of your existing speakers by bringing one of the front mains with you to a store to do A/B listening test against a replacement center. Keep the technology the same, i.e. use silk dome tweeter or metal cone drivers etc. same as the original center has, but pay more attention to the sound. The speaker that sounds just like your mains is the best one no matter what it is.
Option
#2 : Have a shop replace or recone the failed driver(s).
Send or bring the failed speaker(s) to a speaker repair/driver reconing shop. Even if they cannot replace or repair the driver with original equipment, they can almost certainly put in a generic replacement that will work OK and they should be able to match its characteristics somewhat. If you have two woofers in your center channel, consider replacing or reconing both even if one still works OK, to match them, because they probably share the same cabinet air on the backside and the characteristics of such woofers should match. If the shop has a direct replacement, just do the bad one.
Make sure you tell them you want a recone that is physically close to identical. A recone shop once put in a cone for me that rapped the back plate of the motor at quarter power because the cone did not fit properly. My Altec was never the same but there was no choice in that case because the driver was decades old. It had a full range cone with two distinct sets of surround corrugations to decouple the small inner treble radiating surface from the full woofer area.
Option
#3 : Replace the failed driver(s) yourself
Disassemble your center channel (remove the grill if it comes off etc.) and pull out the 'bad' drivers. Sometimes you can tell they are bad before removing them just by pushing on the cone gently (not the dust cap). Usually instant 'rapping' damage of a woofer from a brief high amplitude signal, or a speaker being dropped on its magnet, is because the cylindrical end of the voice coil former is crimped from striking the back plate of the motor, as opposed to melting the insulation and glue on the voice coil winding itself from prolonged overpowering and having the wire buzzing against things. Sometimes both these types of damage occur simultaneously just before the voice coil burns out completely.
If the voice coil is frozen in place or sticking or scraping it can be detected readily but sometimes the damage is not so severe that it shows up this way. You should test any apparently undamaged drivers with a quiet to moderate signal to verify the driver is actually OK, and only test the woofers this way without a crossover in place. Assume the mid/tweeter is OK because of the spectrum of the 10Hz square wave being highly unlikely to have damaged the tweeter.
Be careful not to puncture the cone or rubber suspension with a screwdriver when removing the mounting screws (amazing how often that happens). Be very careful not to put any pressure on the fiberglass/bakelite (or whatever it is) insulator/mount of a terminal or you will snap it right off.
Position everything so that you can place the driver with the cone facing down on a flat surface. Use one (probably slightly wider) screwdriver as a twisting blade lever to pry against the base of the terminal where it penetrates the insulator, and wedge the other (probably narrow and very sharp) screwdriver under the edge of the spade lug so you have something to pry against. Work slowly and carefully because those spade lugs sometimes grab the terminals very, very hard. They have an interlock tab and it takes some pressure to overcome the lock friction.
I only caution you to be careful not to damage a functioning driver. Do not be too upset if you break the terminal off a bad driver. The thing is fried anyway but you might not know for sure until you get it unwired. There might be only one bad woofer if your center is WTW or WMTW or WMTMW.
Even if you do break off a terminal you can still send the driver out for a repair/recone if you need to, or you might be able to superglue it back in place with a paper bandage wrapping to support the glue. Use lots of glue on the inside and outside of the bandage and let the inside glue dry before putting the outside glue on. Imagine you are fiberglassing your canoe.
Look for a replacement driver from your original manufacturer, an OEM manufacturer, AVS Forum classifieds, Craigslist and Ebay etc. classifieds...
You might be able to find a replacement center channel or driver on the wholesale/used web.Try it a few weeks to months before giving up and in the meantime use any old thing as your center channel temporarily.
If you find a beat up cabinet with good drivers that is OK, just make a low bid on it to save some money. You can re-use your cabinet.
You can also widen the search criteria from the original manufacturer and ebay and craigslist etc. to include the other speaker system types within your model line that use the same driver. Use the driver from one of them to repair your center channel. Here is how you find out if this is a possibility...
Once you have the bad drivers in hand, compare them to the rest of the speaker systems in your surround setup to see which ones use the same driver. You might have to pull the drivers out slightly from your other speaker cabinets to confirm. Although my dipoles use the same woofer as the other speakers, the center and mains use a magnetically shielded driver with larger motor assembly. The dipole woofer fits into a center or mains cabinet fine but the shielded driver will not fit the dipole cabinet.
Consider using a replacement driver from Parts Express etc. that has similar Thiele-Small parameters (if you can get the parameters of your old driver) or at least fits the mounting holes and looks similar, with similar cone, suspension, and magnet. Try to sort of match the power rating and absolutely match the impedance (if it is stamped on it). If not you can basically divide the system impedance by 2 (for 8 ohm center with two woofers) or multiply by 2 (for 4 ohm center with two woofers) because they almost certainly either use (2) 4-6 ohm nominal drivers in series or (2) 6-8 ohm nominal drivers in parallel respectively.
Parts Express etc. can probably advise you and might even select a driver for you if you send in the blown one for comparison.
The biggest risk here is that the efficiency of the replacement driver(s) might unbalance bass vs treble. You face that same risk with a generic recone as opposed to exact replacement but at least the motor magnet is identical with a recone.
Sorry you got burned this way. Hollywood should know better. If a bass head wants to listen to 10Hz square wave harmonics (10Hz is inaduble) and feel 10Hz jiggle in his shorts, he can use a PC to create any test signal he wants to. IMO such signals do not belong in a movie because they serve no possible purpose but to damage the equipment of unsuspecting users.