Safety equipment is such a small niche that there are no mega-huge national players as in fast food, retail, groceries or real estate. So there are local and regional suppliers. I don't know where exactly you live, somewhere on the East Coast I guess, but would need more info to pinpoint some suppliers. Or, you could dust off one of those chromatic, multi-gigabyte, random access, cellulose fiber databases and look up "Safety Equipment and Clothing". Or "Welding Equipment and Supplies". Until you get hooked up with the right unit, you should shop where you can get a fit test. That will tell you which size to get in which brand. The fit test will involve putting on the mask and the tester wafting a vial of noxious but nonhazardous fumes at you. If you don't choke and gag, you pass. From then on, you can shop for price.

There are a few national suppliers of nearly everything that handle respirators too. Grainger is one, and the link will access their home page. Search for "respirators" and you will find 134 hits. As you can see, the price range is from under $10 for worthless junk to over $220 for full face units, and that doesn't include the oilless air compressor. For $25-40 you can get good stuff that will last for years. The North and 3M are built easy to disassemble and clean, and that's a big plus.

Scottpacks are a whole different animal, more like SCUBA equipment and with price tags to match, over $2000. And they only last for 20-30 minutes before you must either change the air bottle or get it recharged. though indispensable to guys like Russ, they would be expensive nuisances for most of us.