This sew shop in L.A. https://suayla.com/pages/our-mission was claiming you could use a double layer of common blue shop towels as an N95 filter. I can't find that information on their site anymore.
If it is N95 effective, to my understanding it's pretty equivalent to HEPA air filter standard. It's on my to do list to make an indoor filter this way. If nothing else I hope to reduce the volume of indoor dust that settles in my office. Cheaper than HEPA filters.