Walmart carries two types of worms, earthworms for larger frogs and toads .. and red wigglers, the smaller fishing worms for smaller frogs and toads. They'll be in the fishing section in a little cooler and they usually are never out.

Pop them open and check for soft, unclumped soil. The softer the soil the fresher they are.

Worms in general are a great/safe substitue for crickets and even have more vitamins and minerals.

They also cost significantly less then crickets in the long run and keep longer since you can store them in a fridge.
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I've personally never had a issue with meal worms myself over all my years of having toads and it's good to branch out from crickets. I just make sure to feed the RIGHT size to the size of toad I have. Cane toads for example can easily pass superworm shell fragments, American Toads can handle the medium ones, and the very young toads can easily, easily handle the minature meal worms that you get like 200 in a tub at most pet stores.