At the suggestion of a friend, I ordered wedges from Track of the Wolf for my GPR which had a slot down the center. You take out the escutcheon, put the wedge through it with a small brad or such through the slot and behind the escutcheon, then screw the whole thing back in place. I did have to slip a hacksaw blade in the slot to lengthen it a little, and with the tip of my knife scored the stock where the retaining pin (brad) goes to inlet it. It's harder to describe than to do. The result is a trapped wedge which can't be lost. It works real slick for me.
Also, when I got the GPR the staples were so tight it was a struggle to get the weges in. I had to drive a screwdriver in to open the slot a little. Sounds like you have the opposite problem and need to tap the staple to tighten it up (as suggested earlier).
Cheers,
-Kees-