ThunderPower is the gold standard, and you can get the
newest 70c G8 in the size you need for about 60 bucks direct from Thunderpower.
Maybe when they first came out, but far from it nowadays. What you want in a battery is at least a 30C. Heli's are harder on batteries and anything less than that you are doing yourself a disservice. For price and works good, glacier batteries have been getting rave reviews and nothing negative to date. Just google Glacier lipo's. I know EP buddy.com sells them. As said, stay away from Ebay when buying batteries unless you are buying a well-known brand. Buying cheap lipos on Ebay is a crap shoot.