Here's my solution:

Unscrew the nipple.

Tape a small piece of thick leather over the hole {old belt, whatever}. You can do same over the nipple, but the nipple will carve a hole in the leather after a while and then leave a smidge of leather inside the nipple. No big deal to remove. I do the same for certain auto pistols that have a reputation for FP breakage, wedging the leather in the space in the slide. Works great.

If you need a piece, I have a bin full of scraps!!