The "basic option" would be to find a tiny consumer DVD player (of which there are heaps), which you could fit under the Mac TV quite nicely and connect to composite input. Most of them even run @ 12V so you could even run it off a molex power splitter cable in the Mac TV.

What is the input quality of the Mac TV like? As much as I love my 5500/300 machine, the input quality is at a very low resolution and makes most things (bar retro consoles) look terrible. Not something you'd enjoy using all the time.