As for where I bought mine, I went for the most inexpensive source including shipping and didn't want to bother trying to find one locally in a retail hobby shop.

Got mine from ZHobby.com and had a 100% (customer assistance + speed of delivery, etc.) experience with the transaction.

Just through casual lurking one can come up with multiple hits like this:
http://www.shopzilla.com/7S--Robotic...ord--rc%20tank

A few others have ordered from Raidentech with similar results.

-Harq