There are hundreds of patterns and/or tutorials online — mostly free. I only saw one, on Etsy, that costs anything.
Also, a tip I read that makes sense is to use batik fabric if possible. It’s much more dense so fewer cooties can get through.
Re Etsy. There are many entrepreneurs out there making home-made masks available.
Today I found the batik I bought when it would have looked good on me as a full-length sarong at the beach-maybe the 80’s. I was looking for elastic. I gave it away before Christmas. Still need elastic.
Simple, printable pattern, skip elastic use fabric self ties.
https://www.craftpassion.com/face-mask-sewing-pattern/#face-mask-pattern