There has been some traffic on belts for the the Reeves (variable-speed) drive, for which Clausing wants about $100. I bought these belts from Motion Industries (http::/for about half that in January 2008. One orders over the phone (781-376-5800, which is near me), credit card in hand.
The Reeves Drive belt is Gates 1930V400 and cost $50.
I also got the timing belt that drives the 5914 spindle, a Gates630H150, for $39, because replacing belts is a big deal and so I replaced all belts at once.
I got these two part numbers from other HSMs, not from Motion Industries.