I recently added a 16mm f2.8 Nikon full-frame fisheye to my lens family and wonder if anyone has a solution to the really sub-par lens cap that comes with the lens. It doesn't rattle -- but that's about the best I can say for it. I anticipate it will disappear soon if I don't add a tether or something similar. At least the 14-24mm cap has felt inside of it and there is some resistence to it's sliding off. You'd think after a decade or so they'd have this issue resolved.
I do not have the 16mm but I do have the 10.5 f/2.8 which I believe is similar in size. I use the deluxgear lens cover and it works quite well for me. You might want to take a look at their website at www.deluxgear.com. I believe I purchased it from either Adorama or B&H early last year.
Michael - Thank you for the recommendation. I just ordered one from Adorama. Hopefully it will arrive before I lose the Nikon cap. Since I shoot a lot of industrial stuff, I like to keep filterless lenses covered between shots. I'd probably spend more time looking for the Nikon cap than shooting! Thanks again.
I replaced my stock Nikon lens cap with the neoprene Lenscoat "sock" that B & H suggested as an option; so far, I like it. Another Nikonian mentioned that the Nikon lens cap left scratches on the hood after months of use.