Only plant-based foods have fiber, so your protein will be from a plant source if you are looking for a single food to do the job. The lowly legume is probably your best choice, so something such as roasted soybeans would make a great high-protein, high-fiber snack.

However, plenty of combination foods or combinations of foods could also fill your needs. For example, many sports bars on the market are high in both protein and fiber, for example, the Clif Bar. You can make your own fast, high-protein and high-fiber snacks too.
Here are some ideas that fit the bill:

1. Hummus spread on whole-wheat crackers or a whole-grain bagel

2. A quick bowl of whole-grain cereal with milk and berries

3. Peanut butter on apple slices

4. Homemade bran muffins made with milk and eggs

5. A fruit smoothie made with plain yogurt and fruits

6. Celery dipped in low-fat cottage cheese

7. Yogurt sprinkled with granola