Places I know of...
The 18.61K is probably good for a T4 and Hacker C40. It's $209 at Icare-rc
That's 18 cell and 61+ amp rated. You probably don't need the 18 cell capacity so you could check out the 12 cell versions, but I don't think there's a better choice there anyway.
If you have any local shops there that carry GM stuff you might check out the GM Speed Commander. It is apparently a Knontronik 70 amp car controller. It's $230 at Stormer and Horizon. fyi
I might get one of those... if I can't get a Castle one real soon.