Here are some cartridges that are P100, plus

3M Acid Gas Cartridge/Filter 60922, P100 https://www.amazon.com/dp/B009POHFNC/ref=cm_sw_r_cp_api_i_NGd-EbF2VWH6V

From Amazon, I was even able to set up subscribe and save and get a discount. The other set of filters they sell are set aside for hospitals so we peasants can’t buy them, but these should work for what you are looking for. They should also be easier to clean than the exposed P100.

Good luck!