Your seatpost looks like this one.
http://www.equusbicycle.com/bike/vit...ochure%203.pdf
The mid-80's Vitus used a quill seatpost on their bikes with carbon main tubes.

Googled up a reference by Sheldon Brown to Vitus repair. Perhaps this outfit has a quill seatpost which would work for you.

"Harry Hauvnoonian in Philly (I think) repairs Viti.
The North American Vitus frame facility is Harry Hauvnoonian, at Cycle Sport, home of HH Racing, 801 N. Providence Rd, Media, PA 19063,
tel 610-565-9535."