Remove the screw and nut and take them both to the hardware store. You want to go to a store that has the racks of slide out trays of nuts ,bolts, screws, and a all kinds of other parts. You can match up a nut to your screw or a screw to match your nut. I opted for a pan head allen key screw with a nylon locking nut for my P17. Loctite is a good idea but it's going to be non adjustable because it's Loctited. The nylon nut is a good idea because it's still adjustable but will hold firmly. Hope this helps.
Thanks guys, now about the adhesive (glue). I don't want the nut turning when I make adjustments with the slide closed. What works best on the plastic?
Yes I have it working. If you push on the screw while adjusting it can come out of the hole. But it works. The original screw it too short for the locking nut. I made a new 4-70 screw by shaping a new head but I need to make a screw with a nicer screwdriver slot.Thanks