A number of databases provide access to case studies but they are treated in the same manner as articles and books. When searching the databases, see if the drop down menus allow you to limit your search to case studies, otherwise use the term "case study" as one of your keywords.
There are also a few case study databases:
Some of the case studies owned by these publishers are for free when registering but the majority need to be purchased. Please note that the Library does not provide these case studies.