I found the best deal is a Powerline model that some Walmarts carry. My local one only had the 120v version.
It is a cigarette lighter plugin and it has about 7 tips with it. Puts out 2 or 2.5 amp, more than enough than the A500 needs. The bonus is, it is 4 voltages, 3, 5, 9, or 12V so you can use it for more than the A500. That way you can avoid having an inverter and with your house charger plugged into it...this is a clean device in comparison.
BTW, US company, their tech supported promptly answered a question about voltage range, and that it IS regulated power...think it also has a fuse.
It is the best way to power your A500 or A100 on the road as well as anything else needing 3-12VDC