This probably isn't the best, and it won't give you the longest run time, but the GForce batteries at Value Hobbies are a good option. I picked up two 4000mAh 25C for under $18 apiece. Fits in the granite, but unfortunately does not have a Deans connector. Not a big deal to solder on a new one if you know how and have the equipment, so not sure if that would interest you.
Edit - I tried to post a link to it, but it wouldn't let me. Probably cuz I'm a new member.