Chaps, not everyone happens to have a lathe in their shed or is able to (secretly) use one at work to do their own jobs.* I do have my own lathe in my shed which I use sometimes to turn up a screw or bolt from scratch but if I already have a suitable screw or bolt that is a little too long, I simply remove the required amount off the end. There were 1907 and K98icon grip screws available on eBay the other night when I looked. I would have thought that one of these options would have a good chance of being suitable for the bayonet in question in this thread.

*I don't think that there are many employers who will tolerate their employees doing their own work in company time and using company materials. Things have changed in the private sector nowadays to how things were in the past, what was tolerated in the past isn't so much now.