Just been pondering this. So my suggestion is the following,
Find yourself a bolt that is a tight fit for the hole. Gently insert and tighten for a few threads.
Mark the position on the bolt. Remove and cut off , then cut a slice into it on the top side like a
flat head screw. Then reinstall with locktite , so it can be removed if needed.
Good luck and hope this helps, if you get the idea.
Great minds think alike!
I found a Allen cap head bolt who’s head was an exact fit for the hole.
Chopped the head off, pressed it into the hole and smothered it in JB weld.
Good as gold
Thanks for the replies though chaps, I got there just ahead of you though