old flathead push rod question.

[1927Chevy]

Ladies and Gents

application 1923 Studebaker big six. looking at some sad sack cap bolt type push rods that the valve stems has pounded a hole in. see pics below. is there someplace that sells this type or has someone seen a similar push rod from another application. The threaded size is 3/8 24tpi but the head is undersized with a 1/2 inch hex rather than 9/16. I am thinking I could take a 3/8 24tpi modern bolt and make it 1/2 hex but am wondering about the hardness. how hard should it be?

Ken