Originally Posted by
Unca_Sam
For those less common old sizes, you will find origin8 and uno/Kalloy are the only remaining manufacturer of new in anything other than silver (just black). Scour ebay for the xc post, or search at local co op for a placeholder.
You could consider posting in the ISO thread in C&V with the expectation that you'll trade something for what you need.
You can also find stuff on eBay in the XLC brand. I have a 25.8mm two-bolt XLC post on my old Schwinn road frame. Now that you mention it, my other bike, a vintage MTB, has a 26.4mm (IIRC) two-bolt Origin8 seatpost.
Otto