I've got a Corbin seat for sale that fits my 1992 K75S. The foam is in good shape for the most part but the cover is pretty busted. It is comfortable and usable, but not pretty. At the very least, there is a good seat pan. Corbin told me they would refoam and recover for $250.
I prefer the stock seat, the Corbin is a bit low for me (6'3" with 33" inseam). The Corbin is also too preformed for my taste, I like a flat seat.
Please make an offer if interested. Thanks!
