I was just at a Sam's club and they had a 300 watt power inverter for
$29.95.  I bought it and it seems to work well.  I ran an electric drill, a
100 watt light, my laptop, and my key machine, (all at different times) and
it did well on all those.  It comes with both a cigarette lighter plug and a
hard-wire harness.  Seems like a great deal for campers who need a little
120V!