The diameter and thread pitch can be approximated by fabbing a small wooden dowel of an appropriate size and then forcefully screwing it into the threaded hole by hand. Make it from Pine or other soft wood, tapering the nose and using a dab of wetted soap as a lubricant. It may take several tries before success and it may not work at all but it's better than nothing.

Sorry my earlier collector contact info didn't work out for you, good luck!
Regards, Joe

You can lead a man to logic but you can't make him think. NRA Life since 1976. God bless America!