When I can no find the Bay 60 lens I want, I simply buy threaded 67mm, 72mm, and larger filters, preferably with brass construction, to go onto a brass bay 60 to 67mm thread adapter, that way I can usually find a nice filter from Helio, B&W, etc and use it while waiting to find the right deal on the Bay 60 filter I want for my Hasselblad.
Buy several good bay 60 to, for example, 67mm filters and you can leave the adapter on each lens for more rapid filter exchange, though Hasselblad does no often involve "rapid" photography.
Cheers.