Those optical tracing systems were not brilliant but ok, if I remember correctly it was a Linatrol HL90 but it was a long time ago . The main problem with tracing is the amount of storage space you use up when you want to keep the image for later use. The CMC 2.5 didnt have a great memory. As you say parts for this machine if still available will be expensive, I think ESAB bought out BOC a long time ago, and they arent cheap.
As for fitting pulleys you can easily drill them out on a lathe and simply drill and tap it to take a grub screw and use it to clamp it to the shaft, or you can drill it in position on the shaft and hammer in a roll or c pin to secure it.
Another option is to use a taper lock clamp. These need the pulley drilling out to a much larger size but allow for easy fitting adjustment and removal of the pulley.

Ian