Spam musubi is the ultimate in pack food. Make it up before you go, wrap it in plastic wrap and take it out to eat when you are hungry. They will last a couple of days without refrigeration. A bit of aging time wrapped up in plastic wrap is beneficial. The nori comes in dry sheets and needs some time to absorb moisture from the rice and spam.
Musubi is sold pretty much everywhere here in Hawaii... even 7-11 has spam musubi. Going price, $1/roll. Surprisingly tasty and satisfying. Cheap good eats! The spam-rice-nori combination of flavors is synergistic. Wasabi is not an usual addition, but it's your musubi - go for whatever you think you'll enjoy.