I don't have any idea either. Hope someone has an answer for you. Hugs

I believe the commercial can cozies frequently are made of neoprene. Don't know if this can be readily purchased for a reasonable price. Have you considered Insul-Bright or craft foam?

All About Blanks have some. Just put what you want on them. Also saw some made using Insulbrite between the 2 layers of fabric.

If you like repurposing you could use an old wet suit. A word of warning though I know some who damage their very expensive computerised domestic machine repairing a wetsuit just last week. Her hubby was not a happy man! So please make sure you have a machine that can handle what you sew

real wool felt takes up much water and is isolating, perhaps you can find an old wool sweather and wash on HOT and go on from there

A few years ago...some were using headliner material. Sold at JoAnn's... I don't know how expensive it is now.

Loralye - just Google: koozie blanks and you will see many places that sell the fabric and blanks. I did a bunch at Christmas and just sew up the sides after I embroidered them - everyone loved them!! Hugs, Laura*