I wouldn't be hanging around here, and if  I knew the info, I certainly wouldn't be sharing their names on a fuck board.

Plenty of agencies out there that are underground, and if you have right contacts, net worth, and social status, you can get in as a patron The agency that ex-New York Governor Elliot Spitzer frequented being one of them.

(Or at least, one method that has worked for me)

I know of a couple of providers who are high-end and not on TER.

If you want to find them, you have to do some digging:  Look at the websites of highly-rated, low-volume, yet fairly pricey providers who are on TER (e.g., the ones who never seem to attend M&Gs).  If you look at the "links" section (where banners are exchanged), or their preferred duo partners (assuming they offer that service), you'll often find one or two who are not on TER.  Those are the ones to look for.

Hoe else do they build their business and clientele?  I have no idea, all I know is they must be happy being low-volume.  Many of the girls in this league appear to have (mainstream) modeling careers, so low-volume high-end is about as much exposure to the biz as they care to have, I suppose.

They are all UTR and can't be reviewed.  There are a variety of ways to find them.  For example, some of the big LA-based agencies have UTRs but you already have to be well known to the agency before you can see who they have.  My understanding is they include actresses and the like.  There also are porn stars who are UTR for their own reasons.

nd mix with like minded people who also make that kind of money. The world will open up. Not that I am one of them.

I'm guessing that each side has his/her own super agents who connect the two sides. These agents are available on a concierge basis and keep an exclusive Rolodex.  

If your question is how does a girl get into the club, you'll have to read the ny confidential girls' autobiographies I imagine it's some dumb luck plus hanging around in the right circuits until you're drafted if you've got the goods. I don't imagine they go anywhere near TER.