Band of Brothels: The Circle of Silken Flowers, as mentioned under Platonic Prostitution, along with a couple of its lesser cousins (including the more educational Guild of Erotic Artistry).  In less platonic senses, the Negotiable Affection Division of the Eldinimieuthunimis runs a few of these abroad.  (But even these latter enforce rather, ah, higher standards of professionalism and client selectivity than most.)