I recently started seeing a counselor who specializes in ACT
. (acceptance and commitment therapy) I've found it very helpful. I was moved in this direction by a wonderful book suggested to me by River
called Radical Acceptance
. Also very, very helpful.
My best advice would be to say that any therapist worth his/her salt will be interested in helping you accomplish whatever it is you want to accomplish. I found that searching for a therapist that is poly friendly shouldn't be the goal. The goal is to find someone who will help you be the best possible version of yourself. Be it poly or mono, the therapist should have your best interests at heart.
Be open. Be COMPLETELY honest. And get to work.
Good on you!
Best of luck.