Perhaps my phrase of choice should have been 'trans-aware' as opposed to 'trans-friendly', as you're right in saying it's not 'unfriendly'. I can't think of any people to invite of the top of my head, but I'm sure some research, internet or otherwise, could provide possibilities.
I have also been thinking, the society now has a men's officer and a women's officer, perhaps we could think about introducing a trans-officer. Obviously keeping it a unofficial position (as I believe the other two are?). It may be something worth discussing either at the next AGM, or at the next committee meeting if a committee member wants to raise it .
Just some thoughts of mine I wanted to share