With those prices, my guess would be 'not Kohler'.
I think a Kohler rod through most places is about $80, and that piston is probably north of $200.
Try your Kohler part numbers
here...this place has pretty good prices. Remove the KH and any spaces or hyphens from the part number when you do a search. The last time I bought a Kohler rod from them in 2009 it was $52. At any rate, this is probably the best place to get gasket sets, governor parts, and other random things.