I always say, never ever buy an ac adapter, an extension cord, or power strip that is not certified (UL listed for example) as it can catch fire.
buy a good wall wart (AC to USB) and then get the following....
http://www.meritline.com/5-in-1-usb-...--p-28335.aspx
It will then work with any USB wall wart that's of good quality.