The contact below sell bags of all sizes and shapes and have built in Microporus Filters so no collar and sponge is needed. Unicorn Lou Hsu P.O. Box 785 Water Balley, MS 38965 Ph#:601/675-8000..or..800/888-0811 Fax#:601/675-8800 or. Unicornbag at aol.com Ray Hatch