ktm parts are kinda scarce because aftermarket companies just didn't make parts for them. ktm were enduro bikes much like gas gas are now, and only a few people run them so there was no demand. i got parts for my 94' through White Brothers and after a quick glance throught the catalog i can honestly say your going to have a tough time. it seems the cutoff line for ktm parts was 1990, they don't seem to have anything after that. ALthough you said you needed a 67.5mm piston, well that is the size for the 1990 exc/sx 250 from Vertex Pistons. ANyway, give up trying to find OEM parts and try to find aftermarket.