Cafe Ventana
3919 West Pine Boulevard, St Louis, MO
50% positive
Directions: The bathrooms by the front bar are single-person, locking, gendered bathrooms. They also have a genderfree bathroom: go into the Annex and look for the unmarked door next to Think Tank 2.
Comments: I've also seen men go into the women's room and vice versa without anyone freaking out.