Manual Roof Puzzle-1965 Valiant.

I probably won't be able to see the car again until Friday. It's Tuesday morning now.

The hold-down parts are highly stressed. I doubt polymer printed parts would hold up. Best bet might be to start a request in the WANTED section here.
The first printed parts I used for work was in 1993. I mailed the files on a 3-1/2" floppy disc to a company in Detroit. A few days later I had my parts. Later on, all the companies I worked for had in-house machines. Coolest one was when I worked for a NASA contractor. Big expensive machine that did stainless steel.