I don't have a working battery holder on my Taxi right now, but I want to test the RAM to make sure it holds settings in between power-offs.

I do, however, have an Arduino that I can use to provide 5 volts pretty easily. Could I use something like this to keep voltage going to the RAM for a quick test? I'd try it, but I'm afraid there might be some kind of incompatibility or something that would blow somthing up. Though, with an Arduino, I doubt it.

I went ahead and tested it out. The answer is "yes". Stick the +5v from the Arduino to the banded side of either D1 or D2 and connect the ground on the Arduino to ground on the machine, and you're all set.