After many requests, I am now having built LiPo cells for 2S (two cell) stick packs to support this very popular class (and can be used in many other RC car classes, too).
All the stick packs (~139mm L X 25mm H X 45mm W) come with a Deans connector attached to the pack with heavy multistrand wire for great performance. If you need to adapt the Traxxas' connector to Deans plug, purchase one when you get your pack!
I have several different capacity ratings available so you can conform to your local rules. Average weight is about 250 grams.