I know of no dust mask which works with a beard. The beard breaks the seal between the mask and the face, and dusty air gets into my lungs. There's another way to seal breathing apparatus to the face: the mouthpiece from a scuba snorkel. It seals with the lips, and a beard is no problem. So I made a dust mask with a snorkel mouthpiece. It works beautifully.
Here's a pic of the mask in place. It uses standard 3M filters. In this pic I'm not wearing my safety glasses, but this design is completely compatible with glasses.
respirator1.jpg
Here's a pic from the face side. The green thing has the snorkel mouthpiece in the middle. It is hollow, so there's a breathing passage from the mouthpiece to the filters.
respirator2.jpg
Here's a pic of the two filters, snapped off the green thing. Any of the 3M filters fits. I built the green thing by 3D printing it.
respirator3.jpg