You might check-out sales@yandina.com. I have no commercial connection with them -- but have had two combiners on two boats. Direct prices. They also are sold by Defender and others. I think they also sell Galvanic Isolators. The site used to have a method of checking isolator, I recall.

As for the never switch issues, that works until it doesn't. Hope that it doesn't ever get violated :^))). The problem is not only monetary -- the alternator is instantly dead meat until you get it fixed. Had a "knowledgable" boat dealer that did it to a boat he was showing a while ago. He lost a sale, pissed-off his "client", and caused himself to be the butt of some jokes. I never knew it could be a problem until then.

When we're on a long cruise and something looks amiss, make sure you don't let a "helpful" crew member twist a switch to see what could happen.