You are right! I had air flow issues in one of my cars with HEPA filters.

I just use this. EPAuto CPJ6X (KD45-61-J6X) Replacement for Mazda Premium Cabin Air Filter includes Activated Carbon https://smile.amazon.com/dp/B01LWV2W5M/ref=cm_sw_r_cp_api_i_K9AR887R2BHZGKMZ19EP?_encoding=UTF8&psc=1