We've had to replace SMC parts before, though they all seem to take two weeks to get a part. I found a local distributor, hoping to cut out MHM and Hirsch, but because of the wait, had to go with the more expensive option. Perhaps one of their distributors could help you source out a suitable replacement? Just a thought, but we've had to hack in assorted controllers and what not over the years to keep older equipment running, and there always seemed to be an alternative...
Steve