Try pill bugs and roaches if you can get any. I'm not sure what you have access to. I'd keep trying crickets now and then, too. Just don't leave them in the cage. He might decide one day that he likes them.

What other bugs do you really have access too? Toads will normally eat anything small enough to fit in their mouths, but like Grif said, strictly meal-worms isn't a very good diet. I'm not sure if millipedes would be ok or not. He might eat one if it crossed his path in the wild, doesn't mean it's good for him though. Cane toads are really hearty animals and will normally eat anything in their path.. it's up to you if you want to try a millipede. I know some smell bad and the toad might not go for it.