I noticed the vintage U87 sold about an hour or two after I posted the above, jcoutu1. Was that you, by chance?
I wanted to say... Regarding an old U87 like this... There IS another "quick fix" option that I'm aware of when a mic capsule fades out by breathing on it, and that is to unsolder and then flip around and remount/resolder the dual-sided capsule so that the back is now the front. That can get some extra mileage for you, allowing you to use the back side (which has probably NEVER been sung into directly) which was skinned originally when the mic was being prepared to ship out 40+ years ago. A re-skinning, from what I read of Klaus conversations scattered all over, will change the sound of the mic (and probably drop the value, depending upon who does the work).