These are the lowest head M8 bolts I can find at the moment, but would need the carrier holes taking out to 10mm and a bit of the spacer, to clear the shoulder and then a counter bore at least .5mm deep x 16.
https://www.raceti.com/product/suzuk...olt-m8-x-22mm/
It's sort of what I had in my head when I described a grub screw with a flat head.