Yep, Sybesma's Electronics is the site that I found and then lost. Thanks.

Sybesma is still able to repair these autodimming mirrors. Their price has gone up since the original post on the M-B forum; it is now $175 for US customers, including return S&H.

I removed my mirror this afternoon and plan to ship it to them tomorrow. (The cable connector is a bear to separate. There is no "unlock" mechanism. Just use brute force while trying to not break anything.)

But wait!

While typing this reply to the thread, Scott from Radar-Mirror just returned my call! He is familiar with these M-B mirrors and can still fix them, though he is currently awaiting a shipment of M-B glass. His experience and price of $99 make his service more attractive. I will ship the mirror to him tomorrow, and also send a nice note to Sybesma for their responsiveness.