As I understand it, the Christie "Ultramittent" is pretty much unserviceable. Being sealed, there's not much you can do but replace it. If your company is balking at fixing a soundhead, they'd probably faint at the thought of replacing half-a-dozen intermittents!
Interesting, though. I can't imagine any part in a Simplex or Century soundhead that would cost $2,000. You could get a whole new soundhead (or two) for that kind of money!