Summary

Have amber LED's mounted to a bar (3/4" rigid electrical conduit) on the truck for emergencies or working events.
The cheap original plastic housings became yellow, brittle and 2 have broken.
These look so much better that I will replace all 4.

These new housings are MMU dual-filament, clear and black, to fit around the pipe, and for these specific LED's (cheap chinese set), but any small LEDs could be made to fit.

I printed them face down (like the one on the right) which gave the clear diffuser a nice texture from the bed plate, the pipe radius sticking up, no supports