I noticed that your son is a bit older. Is there a chance of him being a bit self-conscious about wearing big and bright ear protection in public? I'm not autistic, but I do have very sensitive hearing and wear ear plugs a lot at home, in public, and at WDW. I never go anywhere without a pair. I buy mine online from a company that caters to professionals who need ear protection and are very specific with the earplugs they sell in regards to level of protection, softness, ear canal fit. I've also been eying a pair of custom hard ear plugs similar to the ones used for hearing aids. It would cut down on the ear infections and be more cost-effective over time while still being inconspicuous.