smontanaro 

I have a Dura-Ace AX seatpost in decent shape, 27mm diameter. (I think. I saw no size or insertion limit indicators anywhere.) It measures slightly more than 26.8mm, so you might be able to squeeze it in there, but I think it will work better in a 27mm application. (It was sold to me as a 27.2, so I clearly can't use it.) Happy to make several more measurements. OTOH, there are a few zig zag scratches in the bottom 6cm or so, so maybe you will want to sand them out and use it as a 26.8 post. It has a good stencil on one side, not so much on the other. How about $80 OBO shipped in CONUS?

Here's what it looks like:

smontanaro 

:bump: and price drop to $30 shipped OBO.

I concluded that the seatpost was turned down (probably from 27.2mm) in a previous life. I no longer recall where I got it, but I was not made aware of that rather serious flaw. I just measured the round section in several places and got between 26.85mm and 26.95mm, so I think it should work as a 27mm post. Alternatively, you could polish it a bit more and use it as a 26.8mm post.

Here are some photos of the round/aero transition which clearly show where the turning or polishing ended.