You can't do a USB to RCA adapter, simply because there needs to be hardware in between to translate the USB info into a video signal. Sounds like he either needs to buy his own DVD's, or get a laptop, or a portable DVD player. Maybe a PS3 for blu ray support or something like that will work too.
The "hardware in between" is exactly what im asking about. ps3 = to big, to heavy, to hot, to power hungry, to expensive of a peg to fit the hole. its the back of a semi-truck not a 30' pop out rv.
Im thinking more of a mp3/mp4 player with expandable memory and video out(preferably without a screen).
I found something that will work today, i just wish it was a little smaller and a little cheaper. The Western Digital TV HD Media Player!