If trans-related surgeries are specifically excluded, then that probably makes a successful challenge very unlikely, but you never know. You might try doing a bit of research about challenges in general, especially on trans sites if you can turn anything up. If you make enough noise, you could force your insurance company to change its policies. But that takes time.
ChipIn is a good idea. If you can save $2000, then you would need another $2700 or so, right? Have you investigated surgery loans and credit card options (be careful)? What about sponsorships?