I am fortunate. I am able to get the filter from my dealer for $21.50 (9/24/14) plus tax. I usually pick one up if we have any warranty work to get done or need add ons. The dealer is Wana RV in Shipshewana, IN. Hope it is okay to give them a plug because I feel because all their prices on supplies/equipment are reasonable it will be a help to other RV'ers who are within driving distances.
Not sure if they would consider shipping you a couple, but that would add to individual cost.
2014 Rockwood 8280WS
2010 Tundra 5.7 Dbl Cab 4x4