using pi, I measure 28.96mm diameter. I'm guessing that rounds off to 29mm. Was this seatpost diameter standard on old italian bikes? -- My bike is from the 70s or 60s. Guessing its older, but maybe this seatpost diameter can dial in the vintage?

Where can I find longer (200mm+) seatposts in this diameter? -- or adapters for modern seatposts?
I have a lot of thinner alloy posts that are the right length. Would the world's easiest first carbon fibre build project be to wrap around CF sheets around an alloy post? Any other ways of adapting a thinner post?

P.S. were alloy cottered cranks ever made?