Autism awareness merchandise advice

Hello everyone, first timer here. I am looking for something, other than clothing, that my son could wear to make people aware he is autistic. I want something quite bold that will stand out. I am fed up with constantly having to explain that he is autistic when out in public. I feel like walking into a shop and shouting “my son is autistic” to get it out of the way.  Just to save the hassle of saying it to individual people who witness certain behaviours. He wears reins when out and was thinking that maybe attaching something to them would be the best option. Although I’m not sure pin badges would be the best idea. Other than mounting a pole to his back with a large autism flag waving from it (lol), does anyone have any other ideas?  I have bought some wristbands, but unless someone is close to him and looking at his arm, I don’t feel they are enough. Thank you.