[Brandish]

Part? Sure, it's called a 12V battery. Just get a couple of those 6V pop can sized batteries from a hardware store or something, connect them in series and use a pair of alligator clips to connect them to your battery leads (before you disconnect them from the vehicle battery). I've never heard of a deck with an internal battery, probably because in most cases it takes all of 2 minutes to set things up like clock, stations, etc, unless you have an advanced EQ or something.