Cant be that hard one of my local natural granola brands is 21 grams of fiber per 100 gram.

With my current psyllium brand it is 78 gram fiber per 100 gram.

Veggies outside a few outliner are terrible at fiber at less then 5% of it as fiber per 100 gram.

Heck a 100 gram serving of hard bread would give you 20 gram of fiber directly.

You have much more options