FWIW, if anyone is collecting buttplate hardware for a nice synthetic stock that is missing parts, the sling swivel and lower screw on the synthetic stocks is identical to a wooden M14 stock, which in turn is identical to the M1 garand parts. So they are easy to find. Springfield Armory screws are even available from brownells for the lower buttplate screw, and the right upper screw for a wood stock is also available. Oddly SAI doesn't sell the swivel separately, but there are lots of surplus ones around.
GI buttplates are all the same, the wood and synthetic stock buttplate interchange 100%.
HOWEVER...
The upper buttplate screw and nut assembly for the synthetic fibreglass GI stocks are nearly impossible to find. For whatever reason, when you find one, it's almost always installed in a stock. The screw has a unique profile, a slotted head and a 10-32 thread. The nut is just a square 10-32 nut with a piece of sheet metal bents around it to jam it into the recess in the stock. Even if you don;t have a square 10-32 nut, you can just cut a piece of steel scrap to the right size, drill a hole in it and tap it 10-32. You don't need the sheet metal retainer as the nut will stay in place once the buttplate is installed.
The screws are harder to make and basically require a lathe. A more patient man could have copied one exactly, but this one I just made will be good enough to replace one I'm missing. The one on the top is an original GI screw. The IDF sniper stocks re-used this screw, so if you are fixing up an old IDF stock, you're in luck. I have another fibreglass stock that is missing all the buttplate metal though, so although I can order everything else, I had to make an extra screw.
The head under-bevel is 45 degrees, the point on the end of the screw is 60 degrees. The diameter is stepped to match the inlet in the fiberglass stocks and the .210" upper shaft is only a few though under the diameter of the buttplate hole to ensure the buttplate stays centered on the fibreglass stocks, which are generously inlet.
Not my best ever work, but it's a buttplate screw and once parkerized and installed, nobody will ever see it again

The original screws were "rolled" in a mass production fastener die, so they always look super consistent. I made this one by hand (in a manual lathe) out of a grade 8.8 socket head cap screw. I usually make missing milsurp fasteners out of good (larger diameter) grade 8.8 fasteners, despite the metal being harder to machine than something like 12L14 or 1020 mild steel, because you end up with more or less the right hardness and toughness in the finished fastener and I don't have to worry about hardening the end product.