You can write to any player c/o the Sanex WTA Tour at:
133 First Street N.E.
I'm not convinced that this is 100% successful though, but they definitely do forward on mail.
However for Natasha Zvereva I have a better address, I will dig it out at home for you. I'm hoping she is still managed by Terry McQuade of Young Stars, who is based in UK, if so I have his address and you can write to her c/o of him.