You can find industrial grade masks and respirators at safety equipment industrial supply houses to commercial business. Especially look in stores catering to automotive and professional painters. Try the upscale Sherwin-Williams industrial outlets. Any paint store that sells 2-part Urethane paints. Also look in McMaster-Carr on line. You want the mask with the screw-on replacement cartridges with the proper fill, such as activated carbon etc. it wont make you invincable but will protect from casual inhalation.
BTW, I found very inexpensive white 2-part at Sherwin-Williams they sell for water tank lining and bilge water proofing. It did a really nice job below deck and chain locker. Pick the slow cure or you will be hustling.