Update to this post: I started a submission form so that all the FPIES parents out there can share their doctor's info with each other. Hopefully it can help you!
So, we haven't dealt with a GI yet, we just go to an allergist, but I would assume the procedure for finding one familiar with FPIES would be the same...
I was pretty certain that Matthew had FPIES, and had already dealt with feeling ridiculous when bringing it up and being shot down by his pediatrician. It wasn't her fault, she had never heard of FPIES, but most docs (even allergists and GI's) haven't). So, I shopped around (we were lucky, we don't need a referral to see a specialist on our insurance). Here's my suggestion of what you do, based on my experience:
Call and tell the appointment desk that you suspect your child has a rare food allergy, and that you'd like to confirm that the doc is familiar with it before scheduling an appointment. They'll send you back to the nurse, who will either be able to say "Yes, we know what FPIES is" or "I'm not sure, can I check and call you back?" Then either the nurse or the doc themselves will call you back. I would ask them how many FPIES patients they have and what their procedure is when it's time to have an oral challenge in their office .
Going through these steps keeps you from wasting your time trying to educate a doctor and feel all of the embarrassment and frustration that goes along with that. You're seeing a professional who is familiar with the condition and can give you an honest diagnosis, not just a guess.
The first allergist I talked to had one FPIES patient, and she sent that patient to another doctor to do oral challenges. So we called and made an appointment with the doctor that does the oral challenges, b/c they are more familiar with and well equipped to handle FPIES.