You can also use respirator-type cartridge masks with N95 or N100 cartridges.
And I purchased some more N95 facial masks with the embedded exhale valve — makes it much easier to wear the mask while walking or exercising. $2 each in carton of 10.
Picked up some masks locally today, in addition to Ebay order. There is also a P95 rated mask. More expensive. Stops odors too. Wonder if it is better for viruses?