Making staff aware and to be patient

Hello. My brother is Autistic and has a few other conditions that mean it can be hard for him to understand instructions. I took him to a hospital appointment where he was having his eye looked at and had to look up, down, to the side etc and he got confused. He told me this after as I wasn't invited in to the consultant room to assist or reassure if needed.

Is there a subtle way to let healthcare workers know he has a condition that requires a bit of patience. He was very short with my brother that made him frustrated as he can't help it if he's struggling. I know there are sunflower lanyards available but I feel these aren't very subtle. If that's all there is, then I can get him one as he agrees he wants to let people know at the doctors or hospital but wanted something less obvious.

Open to suggestions and thank you for your time.