Any suggestions for a good re-usable ice pack, something granular that will stay that way even fresh out of the freezer? Please, no frozen veggies or similar--they go bad. . .when you forget them on the couch!

I was thinking of freezing pea gravel or smooth aquarium gravel in a heavy, heavy ziplock, with a little water with some alcohol mixed in to keep the water frozen slushy.

Any other suggestions, commercial or home-made?

You can buy reusable packs in the drugstore for less than $5. They can be frozen or microwaved, depending on whether you want cold or heat. They're not granular in texture, but work well for me. They don't freeze solid.