Direct Premium Buys via Amazon offers the SoftSeal Fine Particle Filtration Respirator Filter Mask 10-Pack for $27.60. Coupon code "SOFTSEAL" cuts that to $22.08. With free shipping, that's $6 off list and the lowest price we could find. They feature a 99% filtration efficiency for BFE at 3 microns and PFE at 0.1 microns. They come in sizes S to XL.