Amazon offers the MAVEA Classic Fit Replacement Filter 2-Pack, model no. 1007930, for $4.99. Order via Subscribe & Save to drop it to $4.24 and bag free shipping. That's the lowest total price we could find by $11, although we saw it for a buck less in December. These BPA-free filters fit Brita and PUR systems.
Be sure to cancel Subscribe & Save once your order ships to avoid being billed for subsequent shipments.