"chicory root contains the highest concentration of inulin ... Vegetables such as sugar beets, leeks and asparagus all contain adequate concentrations of inulin. Onions and garlic are also home to a healthy supply of inulin, as are dandelion root, elecampane root and a variety of herbs. Bananas and wheat contain inulin, too."

from https://www.prebiotin.com/foods-provide-inulin/

From the introduction:

“ITFs mostly occur in plant roots, such as Jerusalem artichokes, leeks, or salsify, where they act as a storage and stress-preservative polymer”

More details:

“..subjects were instructed to consume a hot meal for lunch and a soup for dinner, prepared with ITF-rich vegetables to ensure an uptake of at least 9 g of fructans per day (mean intake of 15 g/d)“

The entire dietary schedule is at the end of the paper... but:

'ITFs mostly occur in plant roots, such as Jerusalem artichokes, leeks, or salsify'

I also saw garlic, celery, and scallions in there, but artichokes are definitely an odd one (not a root), while the apparently similar asparagus is missing.

maybe these? https://en.wikipedia.org/wiki/Inulin#Natural_sources