I'm sorry to hear that. I'm sure that whatever you come up with, he'll love it.
Another one that is maybe a shot in the dark: On the website under the Imagination section they had one girl who wished to be in a cartoon. MAW contacted Disney and they made her own character in Dave the Barbarian and allowed her to do a voice over. I know that you said your son is nonverbal, but I'm wondering if there is anyway he could be in his own Barney episode that he would then be able to watch whenever he wanted? Do they even make Barney any more? That might be another one, although it may be a little more complicated than you are looking for.