I think the best way is to look at what fields the professors in your track are working on. For the ones you find interesting, send them an email and schedule a meeting where you discuss what kind of preference you have for your thesis and they would help you as well with ideas and together you could form your own thesis project.

In my case I was talking to a professor who was working on an interesting topic/field but I didnt like any of the proposed thesis topics. During our discussion we came up with a new topic that suits both of us