I have a Tomtom ONE 130 (The newest model, comes after the Third edition) from work that is good enough for my basic needs, and it's under $150 at amazon. It runs on a built in rechargable battery or off a car charger, but I don't think it will run long off of the internal battery, a couple of hours at most.

Tomtom One 130 at Amazon --> http://www.amazon.com/exec/obidos/AS...4GXCBI/tcom-20