Apparently there is a new batting, made by Warm and Natural called Warm Tater. It is just now coming on the market, and made specifically for the tater/corn bags. Here is the description on the Warm and Natural website. I haven't used it, just thought I'd let you know there is something new out there.
"Potato bags are all the rage and The Warm Company has the right batting for all your microwave and kitchen projects! Warm Tater is 100% natural cotton that hasn’t been chemically treated making it ideal for cooking potatoes, corn, rolls and warming tortillas in the microwave. Warm Tater is heavy weight 100% natural cotton that acts as an insulator keeping the moisture inside for fresh, hot steamy potatoes & so much more! Use the free pattern featured on the bolt wrapper or package to create your own. This quick, simple & practical project makes a great gift item! Amaze your friends and treat yourself!"