This isn't really the answer that you were looking for, but this may be helpful.
1. My first SAR-1 had trigger slap. I bought a Romanian FCG from TAPCO in case 922(r) came off the books or I got a U.S. made stockset. I ended up getting a Red Star Arms FCG. Net effect = three extra FCG, after my second aftermarket FCG.
2. Over the years, I ended up with two extra gas tubes, since two of the stocksets I had bought came with one.
3. To this day, I have no idea how I came up with a spare gas piston. Someone must have given me one?
4. I realized one day that I had most of the parts one could conceivably need except an extra bolt assembly, so I bought one.
I realize today isn't like the '90s, but you WILL accumulate some stuff by accident over time.