If you don’t have a specific professor in mind,
Open up a global ranking of universities, such as the Times Higher Education Ranking
Filter by the subject/department in which you want a research internship.
For me, the subject/department was Psychology
Go to the department website of that university
For me, it was the website of the Psychology department of the University of Cambridge, https://www.psychol.cam.ac.uk/
Go through the faculty/lab list of the department to shortlist professors who study your research interest
For me, it was professors/labs who studied social-political psychology: https://www.psychol.cam.ac.uk/research/research-centres