Off the top of my head, only Miss Hunter comes to mind as a SP who openly advertises some sub services. “Submissive” is a pretty wide-ranging term, though, and covers a lot of ground - from rough play to bondage etc.
In general, I have found, for an SP to engage in acts of submission, there has to be a great degree of trust between provider and client. For this reason, very few SPs who are so-inclined will make it public. In my experience, I would say 1 in 10 SPs I have met would venture down the S&M road with a client; and only after several sessions where trust has been established. For example, I have recently engaged with a happy-ending provider, who over the course of several sessions, has opened up about some of her “submissive” desires, many of which she was not even aware. We have gone on a little journey of exploration and it has been enjoyable for all parties. I doubt she would offer these “services” to another client since she doesn’t even offer oral. And this is how it seems to work: you visit an SP, you enjoy her offerings, have conversations, and see where it goes.
Another suggestion would be to enter the swing scene, where there are many a submissive woman. A good portal to investigate is Fetlife.com, kind of a meeting place for social swingers.
Good luck.
