I just bought an imported 95 mm screw-in lens cap which has a fine pitch 'standard' thread. I don't know, maybe 0.5 mm.

I then discovered my oddball lens has a coarse thread (maybe 0.75 mm).

I heard 'modern' Sigma lenses have the coarser pitch on larger lenses but haven't found a source.

I spring-type plastic one would be fine too, but where would I find that in 95 mm ?

Good luck, huh?