I finally tracked down a can of Dolph's EB-41 black insulating varnish.  Red, green and clear are easy to find - but nobody carries the black.

I painted the alternator windings.  This should hold up better than black spray paint; this stuff is designed specifically to spray copper magnet wire windings.

Before:

After:

I stopped at the local Ace Hardware and they had Pony pinch clamps on sale for $1 each; made in USA!  They're the orange handled ones.