Link to the study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2440799/
They even say homemade masks from tea towels to reduce the viral load are likely sufficient. See the end paragraph regarding being too restrictive regarding containment.
Several weeks ago I was in Costco (Seattle area) and they were all out of coffee filters. The next week - the same thing. Then I realized - I bet all of the Chinese in the area are sending them back home to be used as face masks!
I was in Harbor Freight two weeks ago. They had a bunch of dust masks on the shelf. But they are cheap, unrated things. I bought some for some construction dust - they were really bad. (Everyone else is wiped clean). I have what I hope is enough of the masks - but those HF things would be better than nothing perhaps.
I saw that study about masks made from various materials. They found that tea towels and I think vacuum bags were the most effective.
What is a tea towel?