Chuck,
Your problem is a common one among everyone who required glasses and a dust mask. My mom works at an eye surgery center and she said the eye surgeons have the same problem. They take care of the issue by A) pinching the metal around their nose, and then actually taping the mask to their face at the top of the mask - the part where the air comes out.
You'll probably feel a little weird doing it, but it must work if the eye surgeons can do it confidently!
Hope that helps
Ben