Yeah like I own any of those. ;)
I don’t own any, because I have some high quality masks my husband bought years ago. But, if I didn’t have those, and I wanted to make masks, the first place I’d look, would be thrift stores that receive donations from wealthy people. If that failed, I’d call fabric stores to see if they carried a heavy thread count cotton (people used to make their own pillow cases). Failing that, I would bite the bullet and spend the $20 or so, and buy a set of pillow cases. I might see if a friend would go halvesies with me, if I had to. :)