It sounds like of all the suggestions, the dab of CRK grease is the easiest.
As it dries and thickens, it should "gum up" slightly making it harder to rattle. Will wipe off easily when disassembled, too, and be easy to reapply.
I bought a used large 21 Insingo once (still have it) where the previous owner did the cut/ heat/ mushroom thing to the lanyard pin and it did not rattle. I took it out, and put one of the gray CRK lanyards with a narrow band in the middle of it on the knife and it has remained that way ever since.
The heat and squash method worked fine, too though. No reason why it would not work on a small, too, but a dab of grease would be easier, and if it does not work to your satisfaction, then Plan B could be the squash method.