For a nut-free alternative, you could try to make your own bread using a recipe like
this, however it is not grain-free.
You could also use store bought gluten-free bread if you're not concerned with grains and want to make this recipe vegan. You'll need about 6 cups of cubed bread for the recipe.
If you're looking for an egg-free, grain-free, vegan bread
check out this recipe.
You could also try making
socca and using it as a bread base.