If you filled that canopy with construction foam, you could heat some clear blister pack plastic and drape it right over it and get the shape. Mount he canopy so you can pull the plastic sheet rightly, it will cool very fast, and take the shape. You then trim to fit. You have made a perfect plug, so theoretically, you could use plaster of Paris, press the canopy into it, again filled with construction foam, so it won't collapse. Drill holes after it dries to allow suction tunes to be attached. The box could be constructed so that when you press in the canopy, there is an edge you can tape a flat sheet of clear or smoked plastic, turn on the section, carefully heat with a blow drier, and you will be able to vacu-form a clear plastic canopy, which you could spray from the inside to smoke the glass.
This video below shows the easiest way. It's really easy to do, and you have a plug already made.