I have one screen and I need two on a DVD player for the car

This is for a portable dvd player correct?

have a google for http://www.google.com/products?q=7%22+lcd+tv&oe=utf-8&scoring=p
or http://tv.toptenreviews.com/portable/

This unit http://tv.toptenreviews.com/portable/haier/haier-kxt7020-reviews-404.htm has the best feature set per dollar. But you may consider getting another dvd player instead. they can be had for not much more

Unless you REALLY need digital broadcast TV( you are in the USA, right?) then someone's old ntsc lcd tv would serve you quite nicely. all you really need is the video-in function.

The only real trick will be to get a cable with the correct connectors, wired correctly.
hopefully your unit came with a cable that goes to RCA jacks for flexibility.