I purchased a used US Palm grip and it came without the screws / hardware. Anyone provide the correct size bolt / washer it comes with it?  Thx

I don't specifically recall the washer, but if I recall correctly, the bolt is a 20mm long M6x1.0

It's been a while since I had to get one, so someone correct me if I'm wrong....

FWIW I'm looking for the same, I was told on another forum that screw is m6x1-25 or 30mm long.
I had a grip screw in my parts bin from another grip that was the correct pitch & diameter but was just barely too short to start threading the T nut.
I figure if it's a few mm too long I can shim it in the grip.

Only online source I know of is the Fastenal website which has m6-1x25mm but you have to buy a box of 50 for $12 plus shipping. I'm trying local hardware stores first.