Got the the correct 10" tapered, day/night, mirror glass insert today from Paragon Corvettes. It went in very easily. The key is very hot water. Soak the mirror housing in the hot water for 15 minutes or so and the grommet becomes nice and pliable. I then placed a couple of dabs of silicone sealer in the center of the gasket in place of any type of glue that might affect the mirror coating. The mirror pretty much slips in as you gently peel back the edge of the grommet around it. When I got to the corner I used the plastic squeegy and it was easy.
Here's the finished result being inspected by Mr. Noseprint himself...