Amazon offers Prime members the Dr. Elsey's Precious Cat Ultra Premium Clumping Cat Litter 40-lb. Bag for $15.04 with free shipping. (Non-members can spend $35 or more for free shipping; otherwise, it adds $18.62.) That's the lowest total price we could find by $5. This hypoallergenic cat litter purports to be 99.9% dust-free.
Note: New customers can use this mail-in rebate to get their first bag free.