>>2622766One answer is foraging. If you forage and it's not either a fruit or a nut, you can be sure it's pretty high in fiber. As a bonus you get some pretty unique flavors and it's fun.
As for how to start foraging:
Go to a local library or book store, look up the foraging books they have that are relevant to your area. A foraging book about your country or even state is much better than a general one. Different foraging books are different in how they are structured, in a shop or library you can try to look up a few plants and see what naturally makes sense to you. A good book should have clear pictures, a list of uses for a plant and (most importantly) a list of poisonous look-alikes with info on how to tell them apart and how risky each plant is. It should be compact enough that you could take it with you.
As for equipment, I tend to carry a knife, gloves (mostly for nettles or plants with thorns) one of those plastic nets for produce (where I carry the foraged stuff) and a folding shovel, but that's optional and can be done with the gloves and knife as well. Then start learning plants, you'll quickly develop an eye for edible food on a hike.
If you can't be bothered, small prepackaged pills with ground psyllium husk are cheaply available and take up little space.
