After searching ABI Inform, it is possible to narrow results by Document Type. Here you can select Business Case or Case Study.
The Emerald database has a Case Studies tab at the top of the advanced search page. This is also an option on the results page via the facets.
Business Source Premier search results can be narrowed to SWOT analysis publications using the Source Types option on the left hand side.
MIT Sloan produce LearningEdge for case studies covering entrepreneurship, leadership/ethics, operations management, strategy, sustainability and system dynamics.
World Business Council for Sustainable Development: case studies is a collection of studies submitted by companies illustrating how they have improved their environmental performance.