Hi. I think you should discuss with your supervisor first, and ask him/her to introduce someone who is really knowledgeable in the research area. If your supervisor is a well-socialized professor, he/she should have many collaborators and can introduce them to you (maybe as 2nd supervisor). In this case, you have a high chance that you can work on the project with the collaborator for the long-term. Finding secretly new supervisor have a risk that makes professors angry (it often depends on their personality though). And when you find conflicts in the comments between your supervisor and another professor, it's sort of crisis.
However, networking with researchers is really important in my mind and often it helps to accelerate your projects. I hope you will find someone who can help you.