eBay has this RoadPro 500-1000 Watt DC to AC Power Inverter for $19.99 after instant savings. It converts 12 volt DC power into a 120VAC outlet, features 500 watts of continuous power, 2 grounded AC outlets and a low battery alarm. Amazon
has the same item for $39.95 with an average rating of 2 out of 5 stars. Shipping is free.