I use rubber precision pipes (a special kind of
rubberhose).
Diameters for the 9144 are inside 6/16 outside 7/16 inch.
I glue the with polypurethane glue and grind to the right size using
sandpaper 150 (3M wet or dry)
I finish the capstands with a sandpaper 400 so the surface is smooth.
For the HP85 / 9825 /9835 tapedrives I use a 6.5mm citroen hydraulic
rubber.
Someone should concatenate these tips on a web page :)