The 3M 9210 flat-fold N95 respirators are what I've stocked the house and vehicles with. They come individually plastic wrapped, and measure, in the wrap, 1/2" thick, 3-3/4"wide, 9-1/2" long. About the size of an opened empty wallet. One or several easily fit into a briefcase, backpack, fanny pack, BOB. A box of 20 is about $22, I've bought them individually at paint store chains for $2 each.

The 9211 version adds the exhaust valve, which makes longer term use easier. They are twice as thick in the wrapper, and a little more money.

For individuals such as myself who have compensated for a perceived intrinsic lack of manliness by growing a beard, respirators provide little protection due to the poor seal around the perimeter of the mask. My non-NIOSH-approved "solution" to the poor seal is to apply a thick layer of petroleum jelly to the beard before putting on the mask. YMMV. One more item to carry with the mask; one more use for Vaseline.

For lessening offensive odors when the circumstances warrant, applying a layer of Vicks Vaporub on the upper lip/moustache is a help.