Here are a few methods I suggest for reaching out to potential advisors.
Reach out yourself. Yes, it may be hard to get the attention of a professor considering how many emails they probably get on a daily basis but it is not impossible and I recommend you try.
Subject: Prospective Student: Firstname Lastname
Body: Informed questions about their research, reference one of their papers or research highlighted on their website, ask what they look for in a graduate student, *concisely* describe your research experience and interests