I used 1.1mm stainless steal wire at 24 inches .44 ohms in a single vertical loop. You can get it at hobby stores as picture hanging wire. It looked like an old UHF TV antenna. It barely warmed up at all.
Battery size specs are 68mm x 30mm x 20mm. Couldn't find one at hobbyking over 1000 mah and I don't know how much extra room you have. Good luck finding a replacement.