Replacment Cover for Stern Navigation Light

The cover for the stern navigation marker light (white) on my classic runabout disintegrated after some 57 years of UV exposure. Not knowing the brand of the fixture and given its age, I didn't even bother looking for a replacement.

Initially I tried using syvwlch's SCAD thread library, but I was having stringing problems that required too much cleanup, so I hit on the idea of partial internal threads using a pattern of spheres.

I would have preferred to print this in nylon but didn't ha