I'm sorry to hear about your struggles. It makes me so thankful that I work in a very small office and there are two washrooms with no male or female signs. Although by practice men use one and women the other, we also use each others when they are full so it is hardly something that is set in stone or would raise eyebrows. It is comforting...
I honestly don't know what I would do in your place. Part of me would want to battle, but the other side of me would want to work with the others to help them get more comfortable with me. So, I think that I would do a bit of both in a slow, progressive manner. For instance, I would advocate for the retraining side of things so that your colleagues have an opportunity to learn, become more aware, and hopefully a bit more sensitive to transgender and possibly other issues. I would also suggest that there be a team review of any policies around human rights, cultural sensitivity, etc. I would make it clear to HR what I am aiming for but what simple and more change friendly ways could be attempted first because my aim would be for a truly inclusive workplace rather than one forced legally to change. It would only be after this was tried would I be tempted to push harder. I like the soft approach to change first and only going extra steps as they become necessary. If and only when they became necessary, providing I was willing to suffer the potential employment consequences, then I would push on.
Big hugs to you and good luck. I'm hoping that with a little time there will be positive changes for you and your team.
