We didn't want to install a brake box in our SUV so we purchased this wireless brake controller and have been extremely happy with it. We mounted the box on the tongue/frame with zinc screws and just plug in the wireless box into the auxiliary outlet in the car when we tow it (and throw it in the glovebox when we don't use it.)
https://www.etrailer.com/Brake-Controller/Tekonsha/90250.html
https://www.etrailer.com/Brake-Controller/Tekonsha/90250.html