A.A.
My daughter was evaluated through Richmond Kaiser for ADHD a few years ago. Call the psychiatry department and tell them what you're looking for. There is a whole process where they send you questionnaires to be filled out by you, his father, and his teacher. Then there is an evaluation process where they meet with your son (and other children) to ask questions and give tasks while simultaneously in another room talking to the parents about the disorders and how to work with them once the child is diagnosed. I believe they also will follow up with therapy (I am not on Kaiser, so I was only able to have the eval, not the follow-up.) Everything was very professional and thorough.
I would highly recommend reading books on whatever diagnosis you receive before you decide to medicate. They push medication, but I took a different route with great success. My daughter has mild ADHD with some impulse control issues. Most of it has been worked out through switching to a private school, counseling, movement therapy, omega 3-6-9, and lowering refined sugars in her diet (who needs them anyway!) There are also some behavioral modification techniques my husband and I have used that have been helpful as well. I'm not sure at this point that she would be diagnosed the same!
The point is, there are many answers to these challenges that our young ones face and medication is only one. If the diagnosis is ADHD, there are a few books I have found VERY helpful from Western medical perspective to an organic acceptance perspective.
My heart goes out to you. My daughter is also creative, highly intelligent (95% on the GATE test!) but she had a hard time and was difficult to manage (at one point we thought she was deaf because she would ignore us!) I have been careful not to put the label ADHD on her, as I want her to be more identified with her strengths than her weaknesses. However, the diagnosis helped ME a great deal to have compassion and understand that she was not just being obstinate. It is somewhat out of her control.