Summary

Continuing in the tradition of posting solutions to obnoxiously-specific problems, I don't think anyone else here will ever probably work with a "Pflow"-brand elevator button panel where the emergency stop button has broken off . . . but if you do, print this file and fit the 'tube' end over the plastic inner part (it should fit inside the metal outer part, the fit will be tight), twist it clockwise to fit the 'teeth' into the grooves, and you're good to go!

Recommended to print with extra perimeters and and a slightly-higher-than-recommended temperature for whatever filament you use, to make sure it's strong enough to stand up to the abuse that presumably broke the original elevator button in the first place.