CYBERHOME CH-LDV 700B 7-Inch Widescreen Portable DVD Player
It's cheap, but works!
Went to Disneyland, and this little dvd player helped a whole lot.  At first I thought it wasn't working but it was my fault, I hit the button for video output instead of using it's screen.  The battery last for a movie-and-a-half if you don't turn it off and on.  What's great is the car cord and ac adaptor.  The only thing that is annoying is the case, if you hang it on the seat, you have to take it off to put the cover back on, or someone would try to steal it.