I can't answer this question, but I have a recent study done by a University of Vermont historic preservation grad student of catalog homes in Burlington, Vermont. We suspected a large number of extant examples, and she was able to provide the research to substantiate my theory.
We should work to put all the Sears Modern Homes that we know of online. There is a list somewhere, but I forget at the moment. Perhaps your grad student could add his or her work to that. How many Sears homes are in Burlington?
The study was not just limited to Sears. Her work identifies 30+ homes: Some are Aladdin, some Gordon Van Tyne, some from builder's catalogs. Of course some examples are very close variants to Sears models. It was helpful, too, that she was able identify a Burlington office for Sears Modern Homes, as well as contemporary newspaper ads.