Jim -
Thanks for the very helpful reply. Unfortunately, I contacted them and they said that their bass jaws (grateful I now know the terminology) only work on original USA-built Steinbergers and they have no parts for later foreign models. So, I think I'm still at square one. I hope I don't have to buy an entirely new bridge...probably not worth that expense at this time. I'm thinking that maybe I buy one jaw anyway and see if it fits even though they say it's not made for the later models.
Just as importantly, I hope this doesn't happen to any more tuners. I have two 5-string Synapses, one fretted and one fretless, and the fretless model is actually my #1 favorite working bass. If I had to shelve the fretted one, I have a Zon Sonus 5 string that I love...great bass, just not beefy like the Synapse. But I don't know what I'd do without the fretless Synapse...!