I have made two cozies out of blue foam from a pad I got at Target or maybe Sport Chalet-cost $10, if I remember right. I used the rest of the pad for pieces to set my stove on and for a seat pad for snow camping. You can see the pads in various pics I have posted in the winter camping forum a while back.

I used wet suit cement, which works better than hot glue, in my opinion. I made one for a thermos bottle and one for a pot. I just cut out a piece so the handles could swing out for the pot. Nothing fancy, no foil. Not as sophisticated as a manufactured one, but cheap and easily replaceable.
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Don't get me started, you know how I get.