I was poking through Amazon and I ran across a good price on a power inverter. $25.49 down from $59.99.
Sima STP-325 325-Watt Power Inverter
325 watts...but not a bad price. It has a built in low battery shut off so it won't completely kill you battery if you leave it on.
Oh, and free shipping on orders over $25. Hope it helps someone.