Thick noodle soup minus cornstarch/cornflour?
Cook the noodles using as little water as possible and use that water for your soup, or cook them directly in the soup, so that you get all the starch from them.

If that's not thick enough, the only other thing on your list that can really help is the onion and tomato: if you grind them smooth they'll at least add some substance to the soup. You could take it a step further by cooking them down to get rid of excess water and get a thicker paste.