[DonRotolo]

Grainger has several, but 3- and 4-step, all 5/8 bore, more or less same as McMaster.

I work on old lathes, and one trick for unobtanium multi-sheave pulleys is to get what you need as single pulleys (which are plentiful in whatever size you need) and just mount them all on the same shaft, trimming the hub(s) if necessary. Push comes to shove, you can even pin them together if necessary.