A few ideas:
Reach out to a local (or not) university or college. You can do this in a few ways. The first is to contact something like an admissions department or an outreach department. Depending on where in the world you live, the university/college may have one or both of these. Outreach is better, since their job is to connect people in the institution with people outside of it. This may be math students, but it may be a professor as well. Local is best since you can in theory go and speak with the person directly some times, but if there is nothing local near you then you can reach out across the globe. Where are you located?
Reach out to a math teacher at your school. If you know someone you really like, then that person would be a good starting point. They may have contacts at other schools who can look around for you, or they may serve directly as your mentor. If you're looking for a student and not an instructor, this is probably the best way.
Go to reddit. Stack exchange is a question/answer site, so discussions are often discouraged. Reddit, however, is an open discussion site where lively conversation can happen.