Hi!
I put a free pattern online for microwave potato bag makers. Adjust it meet your needs and specifications.
It does call for Warm Tater 100% Cotton Batting. This is
a batting with no scrim; non-chemically treated and great for more than heating potatoes, veggies and tortillas.
Here's the link:
http://www.wholesalequiltbatting.com/a/?p=22