The trans co worker was literally just complaining about it to me yesterday, and my boss literally several times has misgendered him right to his face, like literally standing right next to him.
The thing is I'm getting my Masters in a few months and I'm planning on leaving this job (its just a crappy retail job I do on the side to support myself while finishing up grad school) so the thing is I'm trying to keep my work life as mellow and drama free as I can while I'm still here. I am literally MONTHS away from putting in my two weeks and I have jobs I'm lining up in the mean time. I also have relatives that would let me live with them while I look for other jobs so either way I am getting the hell out of here relatively soon. That being said I'm literally Politics and I feel like I should be doing something to help the cause.
Personally, I'd talk to the manager before escalating it. Nothing accusatory or hostile, just look man, you keep calling him her and it's really bothering him, just bringing it to your attention in case you were unaware. I don't know your relationship with the manager, though, so that might not work.
The thing is its just an assistant manager who is saying this. The general manager is actually a lesbian so I think if I talked to her about it she might be able to do something. I just need to be there a day she is there and he isn't ---