Google search for making a simple IR repeater.. Doesn't take much.. IR sensor, IR transmittor a couple small pieces of electronics and a power supply.
Also you can go to ebay and look for a "VCR Rabbit" These devices worked as follows: The "main" one connected to an AC outlet and accepted input from the output of your VCR. It then, using a tiny 26 gauge wire pair (smaller than the telephone wire inside a handset coil!) it sent the video signal and DC voltage to the slave device in another room. That device could connect to a TV and then display the video signal on CHannel 3/4.
Why do I tell you this? Because the other thing it did was from the slave device, it sent the IR signal BACK over the same wire to the main device which then blasted the IR out of it, bouncing from the wall back to the VCR to allow you to control it from the other room.
Ingenious device actually. And they made RF (wireless) versions too. The wired ones sold for over $100 for the kit, plus $50 additional for each additional room slave device you wanted.
I just saw 2 kits today at a thrift store.. Sadly they wanted $25 each for them. I know on eBay the last couple years, they usually close for around $8-$15 for the kit. You could somehow modify them (taking the parts out of the shells) and mount the transmitting diode directly above the TV's IR sensor, and then mount the receiving one behind your marquee plexiglass or something, and the IR should pass through it.