I’ve been trying to find a host for several UV chips that are at 360-365nm. I can’t use anything with polycarbonate (lexan) because it absorbs strongly. Certain other plastics have good transmittance but I haven’t found TIR optics made with them.
That leaves metallized reflectors, capable of fitting a 7070 chip on a 20mm star.
Any diffusion films on the output again need to be chosen for transmittance at 365nm as well- mostly glass at that point.