In the States, I usually just break down and get the Costco trail mix with fruit. Or stroll down their dried-fruit aisle and make up a custom mix. That's also where I get my favorite: Pacific Gold Turkey Jerky.
I've dabbled with making my own protein/energy bars. I like the Alton Brown recipe (on the web). They're pretty good tasting compared to off-the-shelf bars, but I like them because they kill the hunger immediately without a big sugar crash later. Problem is, they don't keep indefinitely. And you have to buy ingredients in such large quantities that it only makes sense if you're prepping for a big group. But then once I start munching, I can't stop until they're all gone . . . so, no problem.
If AB's bars are too much trouble, there's a company called Matisse and Jack’s that sells a mix for making your own custom bars. Good. In fact, delicious! Definitely better than the homemade AB bars, but more expensive.
If you can get corn flour (not corn meal) try Ultralight Joe's Moose Goo: basically honey and peanut butter thickened with a little corn flour spread on a toasted tortilla. mmmm . . . Some people bake it into cookies and such.
The GF likes those Rice Krispy squares things (simple to make, but too sweet). But then her specialty is deep-fried mac-and-cheese!