[Naturella]

I’m not sure about a high-fiber food, I think both Dr. Tim’s and Nutrisca had over or exactly 5%, something like that.

But, you can always add some canned pumpkin (the plain one, not the pie filling stuff) to his meals, or maybe some flax seed meal. Or some of each. Maybe you could look into added probiotics (from plain yoghurt, plain kefir, or a pill), or digestive enzymes to help with his digestion.