Gunsmithing H&R model 750

[308Gunner]

I need some help I have a friend that brought me a 22 that he is going to give to his little girl, I am needing rear sight screws for this rifle and the smallest I have is a # 6 and that is to big. Can someone tell me what size they are. I have looked at the usual place and they don’t have any and don’t give a size