I have had great luck buying LiPo's and other stuff from Hobby City aka Hobby King aka United Hobbies. I have a bunch of thier Rhino and Zippy LiPo packs, and a cheap charger, and I have had no problems with them. I have a bunch of 2100mAh 3S packs that cost around $20 each.

www.hobbycity.com

I do not know what kind of battery connector the Super Cub has. The packs I have all came with Deans T connectors. If the SC is different, you may have to make up an adapter. I don't like soldering connectors onto live batteries, it scares me.

Good luck


Edit: Oh yeah, I also bought an Aerobird Swift early in my flying career. It was very hard to keep in the air. Once I started flying my glow planes, I took the electronics from the Swift and put them into a Slow Stick.