I have had few problems with my stand-by list for both trips and to keep at work:
Gatorade
Ensure
Pretzels
Flavored rice cakes
Peanut butter and saltines (love the salty combo)
I like to keep higher protein foods at my little fridge at work like hard-boiled eggs too.
Hope this helps you. Nothing is worse than to be on the road, no bathroom in sight and be in pain and have that urgent need.
Good luck to you in life :)