let me know if you find a 12v TV! usually they are all 120v with internal transformers unless you want to tear into one.
Theres some LED monitors that have external transformers that are 12-19V. I want to get a 12V 42" tv but may be stuck with going 120v, they are about 60-80watt draw.
Full HD 1080p Support Widescreen Hi-Res Display Selectable Multi-Viewing Display Modes Built-in Full Range Stereo Speakers Input Interface: (3) x HDMI, YPbPr (Component Video), RCA (L/R) Audio, VGA/PC, PC Audio, RF (Antenna) Output Interface: Optical (Digital) Audio, Headphones Removable ...
Which says "included power supply, 120v".
Some will be 12v others are 19v, like the LG projector I put in my honda odyssey. I wanted 12v but settled for using the 19v adaptor as the projector otherwise fit my needs best. It takes up the space of a book but I hang a poster board behind the front seats and get a bright sharp 45" picture, and can run on its internal battery for 90 minutes.