Gildan 3-ply Reusable/Washable Masks, 48-count, white for $36 (10% off normal price).
I've had these on my radar for awhile, and from what I gathered from reviews, they are decent quality for the price. The interior is cotton, middle is cotton, exterior is polyester. They are 7" wide and ties are 13" long. Many reviews say they are easy to modify with nose bridge inserts. They also have silver and zinc infused into the material for possible antimicrobial action (I wouldn't rely on that theory though). They are imported from Canada. I am hoping I can use fabric markers to decorate them, but if not, then I guess boring white is ok. Good for a small family or a person who feels more comfortable changing them several times daily.
Obviously, they're not medical grade. You can look up the science, and hopefully this doesn't become a bunch of arguments about wearing masks.