Amazon offers Prime members the 3M Aqua-Pure Replacement Water Filter, model no. AP810, for $16.10 with free shipping. (Non-members can spend $49 to qualify for free shipping; otherwise, shipping costs $8.85.) That's the lowest total price we could find by $15. It filters 20 to 28 gallons per minute and provides fine sediment filtration down to 5 micron.