When I was not speaking, my mother used word magnets on the fridge or magnets with pictures of the item the child wanted. This was in the 2000s when technology was not used in my household.

Hi 👋
What is it you are wanting him to wait for ? With my son (also non verbal ) it always depends on what he wants or level of understanding.
How old is you son ? What’s his development like ? My son is 6 and developing at the age of around 3 so I have to remember his level of understanding is at a 3 year old not 6 x

Hi he is 23 years old and nonverbal
He can’t wait to go out for walk but he has to wait for staff to arrive and so two people can safely take him out and two staff can stay at Care Home for other students. Just he can’t wait for half hour or hour