I recently bought a DVD of Prince's video's and I saw his bassplayers using alembics.
 
In the videos for Raspberry berret and Mountains the bassplayer is using a white Alembic spoiler with flower graphics.
 
and in the video for peach, the lefthand bassplayer is playing a Black Alembic again a spoiler but then with a huge amount of pots, flipped over.
 
were these two custom jobs?

Mica has also stated previously here on the site that Prince has several Alembic Custom guitars of his own, but they are all sans Alembic logo as per His Royal Purpleness's wishes, LOL!

Regarding the sans Alembic Logo, the instruments were sold with logo's. Prince made his alterations after the fact.  He also removed company logos from all his equipment.
 
-susan