Camping World has several types available depending on your requirements. I have a dual stage, under the sink set-up that can be purchased at most big box home improvement stores.
If you want to pay top dollar, go to Camping World or any other RV/Marine store. If you want to save money, go to Lowe's or Home Depot and buy the filters, as all RVs use regular household filters.
Bob & Betsy - USN Ret'd '78 & FL LEO Ret'd '03 & FT Class of 2002 '05 HR Endeavor 40PRQ, 400 Cummins -With-'05 GMC Sierra SLT, CC, Z-71, the pusher & our '07 Arctic Cat 500A & '08 Suzuki KQ 400A, riding in the pusher. Where the wheels are stopped