I forgot that I had a metrologist
in the house.
He's measured the parts and has come up with these specifications:
M3 thread, both female and male, with 0.5mm pitch.
Hex bolt body length 10mm.
Male tip extension: 6mm.
Depth of female receptacle: 6mm.
That makes it these:https://www.amazon.com/Uxcell-a14120500ux0242-Standoff-Spacer-Motherboard/dp/B00YM3T88G
Except those are brass. We don't know what the originals are made of, but Fishy says there's some kind of cheap pot metal, whatever is cheapest. I think brass would be fine for this application; I think if I went with Stainless it would be too strong; I'd rather strip one of these screws than strip the part that they screw into on the Empeg. So I'm going to order some and give them a shot.
And don't forget the split washers that go with them:https://www.amazon.com/uxcell-500pcs-Stainless-Spring-Washer/dp/B018TG7DNS
For additional reference, the black faceplate bolts are M3 12mm long, but we didn't get specs for the allen wrench head size. That's probably standardized, so it's likely something like these:https://www.amazon.com/Bolt-Base-Tensile-Socket-screws/dp/B00SN36C6M