I got this charger because it is 10w 2.1a in each USB port.
Plugs in and You can close the 12v socket with it still in.
http://www.cometsupply.com/mp/SCOSCHE/pm/SSOUSBC202M/r/ga/
Note there is a $3.99 fee for orders under $50.
Thought I would share the info/deal.