I didn't know what the source of the trigger guard was so I tried a screw from a Uberti and it fit, so ordered a new screw and mainspring screw for a Uberti. As I said I had to run a tap into the hole to clean up the threads.
The bottom backstrap screw is too long and collided with the mainspring screw, so have to shorten that. Currently I'm working up some walnut.
Incidentally, Numrich (Gun Parts Corp.) lists both trigger guard and backstrap in brass for a Hy Hunter.