I run lights off my rack up high in the rear. They're more often called "dust lights" when mounted to the rear and not necessarily "ditch" lights. Ditch lights are meant to, as they say, shine in front at a ditch. Dust lights are more commonly used more out west in the desert so that the trailing vehicle can see you in dusty environments. I have a pair of Baja Designs S2 Sports Work/Scene lights up there powered and switched by an sPOD. I also use them at night as a camp light as well. Obviously only works if you're hatch is closed. Off my rear bumper I have the same set of BD S2 Sports in white tapped into my reverse lights.

What I'd do if I were you is to get the LFD or Rago roof rack load bars and mount a BD S1 or S2 lights off the rear. They're small, compact, and put out a ton of light. Conversely you could also look into a rack like the Prinsu rack or Sherpa rack. They don't add any height to 4Runner as it's essentially the same high as the stock side rails.