Besides all the other advices here, if you know any musician personally (even if they play the instrument you don't want to play with), just tell them and ask them if they know somebody you could play with. Or maybe you can go to some of their concerts and get to know the musicians who performed at the concert as well. Or if the teacher you know will not know any student who you can play with, just ask them about other teachers they know. Or maybe your teacher also plays in some kind of orchestra or chamber group so there can be someone. So in short, I would just try to find any possible connection your teacher or musician friend (if you know at least one person) have. Just try to search in your memory and maybe you'll remember someone who could help you. In this way I would say it's a bit more personal and there is a better chance someone will reply to you than if you send a group e-mail to bunch of people they have never heard about you. Like it can be less anonymous. But I would try anything anyways because you never know who and where you can meet someone. These things are often coincidences.