Hi,
A year or so back I spent ages trying to find a decent 25.8mm seatpost and didn't have much luck - they seem to be fairly rare. In the end I had to settle for a new basic Push one because they make every size under the sun and then some inbetween. After all the effort it turned out that I actually needed a 25.4! So I've got a spare 400mm one, but I'm afraid it is silver not black. Let me know if it turns out to be any interest to you. Selling for a fiver in my for sale add.
Mikey