Some time back, I bought one of the Coleman thermoelectric heating/refrigeration units that keeps food hot or cold, depending on which way you run the power. I hardly used it, and then switched to the Scion xB. In this smaller vehicle, the big cooler took up half the back seat, and I went for a smaller one that fit the smaller car. I'd about decided to give the original one away, and right about then it came time to test the CarPC on 12V. That's when I remembered that the hot/cold unit came with a 120V to 12V adapter with a socket for a standard lighter plug. Very useful, and it'll run a load up to 5A. Here's the way it looks:
. . . Coleman sells the adapter alone for about $40 on their site, but they're available elsewhere
for $25. Lower-amperage units are lower cost.