Bit warmers

I am thinking about making some bit warmers to sell at a few tack sales here in Wisconsin. If you saw them at a tack sale, would you buy one? I would price them around $10 each.

How they work is they are full of rice. You throw them in the microwave for 30 seconds and put it over the bit and it warms it up for you.

Not my pic, but what I would make