I went shopping eBay for cases for some of my enlarging lenses....OUCH ! The prices some guys want for some of those plastic cases are more than a bare lens. It's almost cheaper to buy a junk lens, just for the case.
Well that puts me back into looking for caps for these uncased lenses.
The only lens that I could "jerry rig" was the Componon-S 105mm, with the cap from a 35mm film canister. But is isn't a very good fit, the cap wants to come off easily.
Looks like I'm going to be buying a lot of caps.