Ooooooh, I think I know what you're talking about. It's an adapter that changes from the 75 ohm coax connector to an RCA jack, right? You can get those from RatShack as well. Look for Game Adapters (remember the Ataris? They used that type of connection.) You may have to rig up a series of adapters; the connectors for the game systems are female RCA to male coax, and I guess you need the other way around. Rat Shack should sell that sort of thing too, though.

I am the Doctor, and THIS... is my SPOON!