What makes you think it is the "wrong" screw?

If the thread is irreparably damaged you would be best to replace the shank rather than the whole locking screw; you'll notice the unusual knurling that will be very difficult to duplicate. Remember the thread it will be some kind of Britishicon thread pattern: Whitworth, BSF, BA etc.

They all look quite original to me, and the wear is probably in the brass female thread, so if the male thread is undamaged you might tin the female thread and retap the hole. Unfortunately, getting the brass turret hot enough for the solder to flow is probably going to discolour it so you might be best to let sleeping dogs lie, or just wrap the male thread in a bit of metal foil, perhaps super-glued on, and pushed into the threads by rolling it between to pieces of reasonably soft wood while the glue is wet. You could also tin the male thread I suppose, if you get it hot enough for the solder to flow well. Make sure you clean the male threads properly first against a very fine wire wheel. That would be my approach anyway.