When I was young and foolish and back packing a lot, I made a lot of portable, low "simple carb" foods. 40 years later, I have forgotten the recipes, but probably ought to return to such foods for other reasons. I recall that granola bars were dead easy, once you got the basic idea in your head; so, I googled around to refresh my memory. Here is an ingredient list that looks amazingly familiar:
1/2 c. honey
3/4 c. peanut butter
3 c. granola or muesli
1/2 c. chopped nuts
1/3 c. dried apricots or raisins
1/4 c. toasted sunflower seeds
1/4 c. coconut
1/4 c. wheat germ
1/4 c. toasted sesame seed
The trick was to boil the honey for a while, not long enough for "soft ball" or anything, but long enough to have it cool to being a little more viscous than raw honey, then dissolve the PNB in it. Once the honey/PNB mix is combined, you add approximately 5 cups of healthy, high fiber, complex carb "stuff", mix (and think of rice krispy treats, because the process is the same), press into a greased or nonstick 9 x13, cool, cut and wrap.
The 5 C of "stuff" here is a good starting place. I think I was cheap and always used a couple of cups of old fashioned oats, toasted on a baking sheet at 375, though a good granola always played some part. I am partial to dates, so I know I used those in place of the coconut sometimes.
In the bottom of a backpack, these may be more mounds than bars after a few days, but tasted fine. They are stable in a more stable environment, lol.
...ya know, I bet that someone with a spa type restaurant could press the mix into a small bowl shape, fill that bowl with Greek yogurt, garnish with fresh fruit and have a real hit...