Directions: There are 4 entrances to the building(s) around the courtyard, so make sure you enter Reuvensplaats 3 specifically. Once you're inside, go around the corner to the left, go up one floor on the stairs on your right hand, and make a u-turn at the top of the stairs. You'll see the all-gender bathroom on your right hand side.
Comments: Two seperate stalls behind the door with the bathroom sign, both have bins. This is a University building. It's a bit more quiet than the other buildings, and I'm unsure whether there are actual lectures/workgroups there. If you want an excuse at the ready (especially without a student ID), you could say you're supposed to meet with a friend/sibling/kid/... there. Then again, I don't think people will generally ask for your reason to be there (unless you look really lost)