Scotts like many others used some obscure threads . British Cycle threads, American sewing machine threads .metric threads ,the list goes on. It will be far simpler for you to do what I and most of the other gunsmiths I know and simply tap out the hole to the nearest modernd size .We use B A I think the US has a similar range , then make a new screw or I should say pin to fit. I'm afraid the chances of finding a pin that will fit is vertualy impossible.