I just picked up some of these packs for my Xray M18T. Can't comment on the performance yet, but for the price I think they are worth a shot. The little pics in the middle of the listing show them fitting perfectly in the Traxxas mini.
As a note, the first pair I ordered were like pictured with the removable leads, then I ordered a second pair which said "V2" and had permanent leads on them. Other than that they are identical, but if you want one type or the other might be a good idea to contact them first.
http://cgi.ebay.com/7-4v-1800mAh-30C...item4cebbf0ed5