I'm by far no expert and you may have looked into this already, but did you see if a remington pro 88/pro 88G piston would work? Also guys have said some of the homelite and remington stuff can interchange. Not sure if it helps or not, just those saws are so rare that I would love to see another one resurrected. Good luck on your saw @Yukon Stihl.I have a 990 apart till I find a suitable piston too on bring it back too life.