Trying to power something powered by a car (120V) via an AC outlet (120V). What's the best route?

Question

Have a device typically powered by a car's electrical system (12V). Want to power it outside of a car, but not with a battery.

Considering:

http://tinyurl.com/6pdpys

http://tinyurl.com/6c52sd

Not sure which would be more appropriate? Anyone know how many mA is best for this application?

Is there a cheaper/better way? I'd even go USB, but that's only 5V iirc, which wouldn't be ideal.

Answer 1

What sort of device is it?  My GPS can be powered from the car's 12V system or a USB, so it's not impossible - it all depends on the device.