As the lovely Phyl said, there are many doctors around Boston with significant AN experience. An AN is not, generally, an emergency situation so you have time to talk to different doctors, discuss various treatment options (including not treating immediately), and figure out what you want to do given your particular situation.
Honestly, I wouldn't call Dr. Barker directly. He's a neurosurgeon and will want to cut it out, and isn't that great at the interpresonal stuff (though an amazing surgeon). My experience was that McKenna was great at weighing all types of treatment options and helping you come to your own decision, which isn't always surgery. McKenna is making appointments for Oct if you call the office. And given what you've told us, I'd be very surprised if waiting until Oct would pose a medical issue. ANs are usually incredibly slow to grow.
There are also great doctors at Beth Israel, Tufts Medical Center, and probably elsewhere in Boston with great AN outcomes. I'm sure if you ask others will be happy to give recommendations to give you choices. Don't be afraid to make appts with several doctors and see what you think after talking to all of them. The treatment of ANs has a lot of variability and choices based on individual circumstances.