12VDC TV 's are available...just do an internet search.
We have a 15" Naxa brand from a mail order warehouse...it was very afforable and is actually AC/DC with 2 power sources.
http://www.irv2.com/forums/f121/outl...ml#post1717156
And, there are many TV's that run on 12VDC...sold with a wall wart transformer (external power adapter) like many models under the Insignia brand at Best Buy....affordable and available. All you have to do is make a 12vdc power cable for it.
I generally stay away from all-in-one electronics, because when one part stops working, you are replacing 2 pieces-in-one
A stand-alone DVD could be a very inexpensive thing if you look for a portable DVD like for use in a car...just plug it in to the RV's system as you would any DVD. But, portables typically have 3 way power AC/DC/Battery.
Best luck