PetSafe® Drinkwell® Replacement Foam Filters at Menards®
Amazon.com: PetSafe Drinkwell Replacement Foam Filters Compatible with PetSafe Ceramic and Stainless Steel Pet Fountains, for Water Dispensers, 2 Pack - PAC00-13711 : Pet Supplies
Premium Charcoal Filters for PetSafe Drinkwell Fountains - Walmart.com