<there is none anywhere I know of that are ground and diamond=20
  POLISHED.  The auction is for 50 of them <
  
I use the shafts salvaged from capstan motors from VCR machines, =
they=20
  are Tungsten carbide approx 50mm long and 3mm diameter and =
Very=20
  highly polished ( mirror finish )
  
Check your local electronics repairer ( if they exist in your =
area :)=20
  dying breed nowdays)
  
Dale