Perhaps need to clarify ..
it looks as what is called a " pipe pin " not sure what the English word is
the hole is slightly smaller than the pipe pin
pressing it in it grips and sits.
But with a shop drilling machine where it can be held firmly in a fixed position and adjusted so the drill
goes in perpendicular and the right size drill it will come without hitting other things.
Perhaps a locksmith have something or a gun repair shop.