While I thank ThinkGeek for their idea(I can't believe I didn't think of this first), I decided to make my own because I found a flaw in their design: Their sleeping bags are for indoor use only(you could not actually survive a night on hoth!) thus defeating the purpose of having a trusty tauntaun in the first place.
Therefore I have created(with a lot of help from Mrs. ihrtglfx10) my own version of the sleeping bag using an old Trekk bag that is rated for -20 C so this model can actually be used for camping trips spent in frozen wastelands. It is being given as a Christmas present to the next generation of geek, my nephew, to help him survive winter in the Colorado rockies.
Please message me if anything isn't clear or you need advice/tips/hints with your own tauntaun.