You can wash and reuse the factory foam filters. But I have seen some replacment HD filters for RV AC units. I like the ideal of filtering more dust/pollen but im not sure if that would reduce the air flow too much and some of them are expensive. Might be better off finding a cut to fit some sort of HD foam filter at HD or Lowes.
2017 Axis / 25.4: Big Foot Levelers, Aims 1200 Watt inverter, Ceramic Window Tint, Full River AGM 6V batteries, Front Hellwig Sway bar / Rear Track Arm, Safe T Plus Steering Stabilizer, PD 4655 converter, Hard Wired Surge Guard, WEboost + WiFi Ranger, LED Headlights/Driving lights, TPMS, Surge tank, Tornado flush, Viair Compressor