If you are really lucky, your cable box has a 1/8" TRS jack on the back labeled 'IR'. If so, pick up one of these: http://www.amazon.com/HDTVHOOKUP-Dual-Frequency-IR-Receiver/dp/B00255GURK/
I'm not recommending that particular model or seller...that was just the first one listed when I searched for "IR receiver". They vary in price, size, geometry, etc. There is also dual band vs single band. Personally, I couldn't get single band to work with all of my gear, and the dual band ones aren't much more expensive. Just fish the cord and plug it in. If it works, it will be the simplest, cheapest, and most reliable solution.
If you don't have an 1/8" jack, get something like this: http://www.amazon.com/gp/product/B001BLTDZA
I can recommend that model. I have four rooms feeding it using 50'-100' lengths cat5, and it works seamlessly. For a back-to-back fish, the cords on the receiver are long enough that you probably won't need to splice in an extension.
There are other aesthetic options too, like: www.amazon.com/Cmple-Repeater-Sensor-Receivers-Frequency/dp/B00255HQXC
You just match up the +12V, SNG, and GND wires on both ends. You can also pop the bezel off your TV and put a receiver inside next to the TV's sensor if that's your style.
If you have a plasma or LED tv and are unlucky, you may need to position the receiver so it doesn't catch any direct light from the display.
If you have an AT&T U-verse cable box, do more digging. I have read that they don't play well with standard IR gear.Edited by EricN - 10/3/12 at 3:55pm