Where do you live? If you are in NSW, I'd think Dr Robert Jones (neurosurgeon) at Sydney Children's Hospital in Randwick would be a good person to see for a second opinion. He was apparently one of the pioneers of the helmet therapy. If you're not in NSW perhaps you could phone the orthotics department of whichever hospital near you makes helmets and ask which neurosurgeons prescribe helmet therapy through the hospital. Then you could get a referral from your gp to one of those neurosurgeons and see them privately.