I figure non-corporate sites are not going to draw from a single domain.
I think the confusion is understandable, as the above quoted text can be re-written without two negatives to read "I figure non-corporate sites are going to draw from multiple domains."
That said, I suppose it's pretty clear at this point what mraeryceos desires:
I am looking for sites that only use one domain.
Whether these sites are "corporate" or not is immaterial to the request, and IMO that nomenclature isn't helping the discussion. That said, I think 4wd got it (mostly) right the first time and offered an adequate response with good suggestions. It may be possible to use some kind of a blocker such as uMatrix to block any attempts a site makes to connect to 3rd party sites. But it doesn't seem feasible to filter search results, especially Google search results, to list only sites that don't attempt to connect to or load from 3rd party sites. You'd have to load each page in the search results to see if they connect to anything else. And possibly go through thousands upon thousands of them before you got even one page of results that met that criteria.
At that point you might as well be making an internet archive. In fact, that may be another alternative. Use a site like https://archive.md/
to archive any page you want to visit. It will archive the content on its own servers and serve a static page.