Well I didn't find one per se @funbobby51 , I booked a telehealth appointment with my regular doctor's surgery / General Practice which i've been seeing since i've lived in the local area.
They had over 3-4 years of my medical history on their patient records and although there wasn't anything in there too extreme that would exempt me immediately (such as a chronic lung condition) there was enough prior medical history for me to substantiate very easily why I required an exemption.
Put it this way: wearing a face mask is bad for your health. If you are in a state or frame of mind which a fact like that will really weigh on you, then being forced to put one on is causing harm to your health mentally (and physically).
Here is a hypothetical situation: what would a doctor do if you said you will commit suicide or stop breathing if you were forced to wear a face mask. Would they be compelled to exempt you? Would they use their better judgment and medical know-how to diagnose you with whatever it takes to preserve your life?
I have a sticker that I got from the zoo and made copies of and no one ever questions it when I wear it.
From the zoo? What does it say?
"Do not feed the wild animals"
heheh
It says "Health risk- unable to wear mask" and has a heart on it. No one ever questions the sticker, if someone says something to me about a mask I just point to it and they apologize.