If you want to make your own real inexpensively buy a toothbrush cover. Walgreens has them in packs of 4. Get some green floral foam. You can get that real cheap at any florist. Cut the foam to fit into the toothbrush cover, fill with water, shake excess off & dry outside with a cloth. They work very, very well. They are small. Mine are only 1 1/2" x 1". I use 2 of them in my tenor case. I made 4 of them for about $5.