Mu 2 Sport Mask (Washable - does not use replaceable filters).

http://www.betterfitnessproducts.com/mu ... smask.html
Harbor Freight Carbon Filter Neoprene Dust Mask With Replaceable Carbon Liners (Additional liners are hard to find and not on the web site).
http://www.harborfreight.com/multipurpo ... 94222.html
RZ Mask. Uses replaceable filters (Hepa and/or activated carbon) that can be purchased from website. Just be sure to scroll past the ratchet straps to see the masks. Comes in multiple styles and colors.

http://rzmask.com/shop/
They all work better than a handkerchief or scarf, and are more comfortable than a construction dust mask or full on respirator.