I get the vibe that new Rivendell frame sets no longer come with a seatpost. I bought two Rivs in the last couple years, both of which did come with a Kalloy 26.8mm seatpost. I splurged on a Nitto for one and a Dura Ace for the other, and these are extra. Rivendell retails them for $30, and I think everything second-hand should be half-retail, so these are available for $15 plus shipping, each. They are 300mm long. Unused, uncut.
Bill Lindsay
El Cerrito, CA