I'd be really hesitant to use any of my clothing as a freezer bag cozy in bear country! I have managed to spill the food while stirring enough times that I keep my cozy in my Ursack at night.

My cozy is made out of a couple of pieces of an old closed cell foam pad and some duct tape and weighs less than an ounce (I'm away from home so don't have the exact weight). I found the directions somewhere on the Internet but since my "bookmarks" have been wiped out twice since then, I couldn't tell you where. It might be on the same site as the "Super Cat" stove, because I was looking at alcohol stove ideas when I found the design.