I typically like to buy simple stuff from Amazon ..because you get to read some reviews. Boy were the reviews bad for these plug-in chargers!
I got one off Ebay (item #270638016141 by seller 'crazyonmp3') .. it said the right things about spec, but you never can tell... Still, for $5 - with free shipping .. eh, WTH.
It works. I've taken the iPad to the beach before to watch radar, blow time waiting for wind, etc .. only to see I had 23% left!
I will never have that problem again..