Where can I get a rice sock?

I'm preparing to start home testing, does anyone know where I can get a rice sock?

 

We make our own by taking an old, clean sock and putting about a half cup of dry rice in the toe and tying it off. You then microwave it long enough so that it's very warm but touchable.

 

Thanks!

 

Just as easy....fill an old pill bottle with Very warm water, cap and place against ear. Works well for me!