Found this from 2002 - any new products that will do what is asked?

Hi,

I'm looking for a portable TV tuner, battery operated, that I can
hookup to my portable DVD player.  In other words, the TV tuner needs
to output a video and audio signal, via RCA plugs or 1/8 inch audio
cable, so I can input the signal to my LCD monitor on my DVD Player.

They make several of these types of devices for computer monitors and
computers, however I have not located one that is battery operated.  I
have located a Citizen M329, which is exactly what I need; however it
only works on the PAL Broadcasting Standard (Japan) instead of the US
Standard NTSC.

At this point I would even except instructions on how to remove tuners
from portable TVs so could use it with my DVD player.  (It seems all
Portable TVs only have a video-in port and not a video output.

Good Luck!

Polaroid made a dvd player that included a battery-operated tuner.
Here is some info on it from a product disposal company:
http://www.shopxscargo.com/product_catalogue/cat_product_details.asp?category_id=6&product_code=22856&sub_category_1_id=18&category=Video

I wonder if the portable TV tuner that was made for Game Boy might meet your needs.

http://www.gameboy-advance.net/accessories/gba_tv_tuner.htm