Most of the concepts of the Hamberger sound post were covered under patent 5,208,408 awarded to James G. Cave on May 4, 1993.  I purchased the materials to make an articulating end carbon fiber violin sound post (carbon fiber tubing, solid carbon fiber rod, and a carbide ball ended milling bit) inexpensively from China, since small carbon fiber components are widely used in the radio controlled air plane hobby.  The thing that stopped me was how to accurately make ball heads (item 29a and 29b shown in the patent illustration).  I finally found a source for metric bead chisels on eBay and they are now being shipped from China.

I don't think that the ball ends in the sound post should cause any buzz because the sound post is always acting in compression.  It is the bass bar side of the violin that is vibrating.  At least in theory.  I should be able to tell you empirically in a month or two.

The tricky part is going to be the retention of the balls within the hollow created in the cylinder.  I was thinking about using ball bearings and and retaining them on the shaft with "horse shoe"  type magnets, and pulling out the magnets once the sound post was in position.  The other option is to use o-rings, but I am concerned about the muting they might have on the system.