Via the blog
Nuts are always great; peanuts, almonds, cashews, walnuts, and pistachios are easily transportable sources of protein.
Although all nuts should be stored in the refrigerator (to slow down rancidity of fats), it is certainly okay to carry some with you throughout the day.
I am not a big fan of protein bars. The vast majority of them are loaded with added sugar and saturated fats.