You should be able to locate case studies using the ABI INFORM Global database by combining subject terms "case studies" with terms related to your area of interest.
You can also search for case studies from the Harvard Business Review using the Health Business Elite database. Just add terms related to your area of interest to the search field.
There are also commercial publishers that produce cases for classroom use; these are available for purchase (typically priced at about $8-10). You can search for cases at these sites using the links below: