i have seen car-type media players that meet your needs-- you just load a SD card with the files, and then play them off of that.
there is also devices like the WD Elements box-- it has a 1tb hard drive for media, analog video/audio connections. the down side is that i believe it requires 19v power-- which means that you need a power supply like the carnetix 1900, 2140, or other models like the dc-dc usb.
now that i think about it, there should also be external hard drive cases that have what you need as well-- i know i have seen a couple in the past..
like this one: