I wonder if one could use corn starch for some of the thickening effect - other seasonings to make up for the flavors in the soup - probably need to read the sour cream labels carefully, too. Some of them have a lot of "stuff" in them.
Or rice starch. There are other thickeners out there - if one can tolerate them and the rest of the components.
One of the few advantages to cooking "from scratch" - one has a better idea of what one is putting in one's mouth.