Just learned this today while ordering some pre-filters and replacement SAS Bandit respirators from Eastwood:
http://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/The pre-filters for the Bandit are R95s; which is really handy for working on things other than straight paint - even if the mask is only good for N95.
I have had really good success with this piece of kit.