David:

Do you have the flange for the back? If I recall correctly, you have to tilt the mirror all the way down and then insert a flat blade screwdriver to slide a lever, which then releases the mirror. If you could get one of those flanges or if you have one, then you could probably get a replacement mirror cut. This is pretty thick quarter inch glass, with rounded corners,  and then they apply a slight chamfer to the edges. You would probably need a diamond coated wheel on a stationary disc sander to round the edges properly. All in all, probably a fair amount of work. If I recall the replacement glass about $75? What's your time worth?

Troy