Depending on how many connections you need, these can be relatively affordable or insanely expensive to have someone do (I got some quotes that ran upwards of $600). If all you want is 1 (or 2) HDMIs, 1 component, and 1 VGA, I would get a regular old 3-gang backless box, a regular old 3-gang decora-style wall plate and the HDMI Decora insert, the VGA Decora insert, and the Component Decora insert from Monoprice and "make your own". That's certainly the cheapest and easiest way to do it. IOW, I'd piece together something like this (note that this is just an example; I don't have any experience with these vendors other than Monoprice -- whom I wholeheartedly endorse):
HDMI Insert: http://www.monoprice.com/products/pr...ormat=2&style=
VGA Insert: http://www.cablestogo.com/product.as...2713&sku=37052
Component Insert: http://www.monoprice.com/products/pr...ormat=2&style=
I personally wanted my wallplate to "replicate" my TV inputs behind my A/V cabinet AND be the terminus for all of my speaker runs AND contain my source cables (cables from the dish, the OTA antenna, the phone system, etc.). So, I ended up getting this and piecing together my own (like described above only on a somewhat larger and more customized scale):http://www.partsexpress.com/pe/pshow...TOKEN=99764325
That wasn't cheap, though. All told, the plate with all of the inserts ended up costing me a little less than $200 in parts alone. You can check the "Parts List" here to see what I used: http://www.avsforum.com/avs-vb/showthread.php?t=902002
Anyway, I would check Monoprice and see if they have what you need. If you need a greater degree of customization, I would also check Ram Electronics and Parts Express. Between those 3 vendors you should be able to piece together pretty much anything you can dream up.
P.S. FWIW, many people dislike the concept of a wall plate because it interrupts the cable run. That is, it's better to have one, uninterrupted cable between your source and your TV than it is to have a cable from the source to the wall plate, wall plate, cable in the wall, wall plate, cable from wall plate to TV. I'm not 100% sure of whether or not that's true, but it makes sense to me. I, personally, "compromised". I have my a wall plate behind my A/V rack, but don't have one behind my TV (cables come through a 3-gang recessed pass thru style plate). To each his own, though.