My dog eats the Blue Buffalo Natural Diet Dog food that I buy from chewy.com
He loves the Blue Buffalo Dog food and it helps with his GI tract and it's very high in fiber.
Other good high fiber dog foods are, Taste of the Wild Dry Dog Food, Wilderness Blue Buffalo High Protein Dry Adult Dog Food, Earthborn Holistic Dog Food, Natural Flavor, Nature's Variety Instinct Healthy Weight Grain-Free Chicken Meal Formula Dry Dog Food.
I'm sure there could be many more high fiber dog foods but those are the ones I know about.