The cat is out of the bag!
BLUE SHOP cloths. (COSCO has best price)
Yes, that is what I make mine from.
For elastics U can use the ones that come from bundling fresh vegies at the supermarket.
In fact I made masks simply using my office stapler to create the folds.
Also you should note that the manufactured masks use 3 plys.
One sheet of shop towel folded will make a 2 ply easily so take 3 sheets of shop towel and cut in half so you get 2 masks from each 3 sheets.
Since these are 'throw a way' masks the stapler method is more than adequate INMHO
Main problem is the void around your nose area. I suspect a soft 'clip' or dabbing of hot glue could create a nice 'springy' nose clip.
A clothes pin works but they are too tight. LOL.
I got the blue shop rag idea as that is what I use on my shopvac to pick up gyprock dust and that's ultra fine dust!