no they don't carry that in most hobbyshops, since low-end packs are pre-made, and high-end packs are not shrinked, they are left open so it can be discharged on a tray (mounted side-by-side).
You still can ask them to order some, but I found that the one carried by onlybatterypacks.com is good enought. you need a 3" or so shrink.
here is the link:
http://onlybatterypacks.com/showitem...temID=11091.38