I have made the lens cap.
The bit of metal which I cut out originally for the hood, (and rejected because there was a drilled hole in the side) has come in for the cap. It was just big enough and there was just enough thickness to make the cap.
Chucking such a delicate thing in the lathe was something of a challenge but I got there.
This is the lens front with the cap, which still need painting, the 16mm fisheye lens in the background.
A self portrait?
...and sharper! Could have looked happier...
Am going to get a piece of black vinyl cut to match the 16mm lens cap with "Nikon" in the middle.