is there a transgirl dating option?
Gabby was probably designed the closest to that in that she can have a dick, though maybe not exactly what you were hoping for.
In the PC Feminization storyline with Chloe you can get her to have a dick later in the story, as well.
Besides that, I guess there hasn't been a traditional transgirl character option, so it might be a good idea for a character in the third town.