Data - think about what data you can actually collect and narrow down a topic based on this
Case study - base your research about a specific organisation
Action research - identify a problem that needs to be solved
Replication study - take someone else's research and apply it to a context that you can access
Systematic review - a broader thesis based on existing published research - there is a recent special edition of the Journal of Business Research on systematic reviews which includes 13 articles
finding a research problem worth exploring is not a quick and easy job. You need to read a lot of both theoretical and empirical prior research in order to get there.
If you find some mixed findings, your study could explore the reason for such findings. A contingency approach is quite useful there.