Just buy the cells cheap and have someone on RC-M build the pack for you on the cheap.
I'd offer to build it, but you probably shouldn't trust the packs I build. I think lincpimp and BrianG both know how, and I'm sure there are several others that would be willing.
I just purchased two 2S2P A123 packs (6.6V, 4600maH) off ebay for just under a 100, and I bought one of those 'Daptors....thanks kulangflow for the link. I'm going to send an email to MRC to see what they have to say about the 'Daptor, and how it might work.
Losi 8T 1.0, Savage Flux - XL style, LST XXL, Muggy, 3.3 E-Revo Conversion and sitting outside 425hp, 831 Tq Dodge Ram Turbo Diesel. It SMOKES