Here's what I'm using and can't tell you how awesome it is!
1C rating so months between charges, less than a tenner and in stock in the UK. What more could you ask for?
http://www.hobbyking.com/hobbyking/s...arehouse_.html
Important Information - Read this bit >
The lipo comes wired up for Futaba/JR, so you need to swap the wires in the plug to the configuration shown in my pic.
Of course, swap the leads one at a time to avoid touching the +ve and -ve together as
THIS WOULD BE A BAD IDEA WITH SMOKE AND LIGHT EFFECTS! 
Other than that it's plain sailing. My Gemini II is currently showing 12.2v on a full charge. Drops off in use to around 11.5ish but then just sits there forever...
Martyn