Some of us with rear trailer hitches on our RVs have added a 3rd brake/tail light to our rigs, fits in the 2 inch hitch receiver on the back of the RV. Plugs right into the 4 prong trailer hitch wiring plug. I've wanted to get one and its a cheaper alternative to adding more rear tail lights and wiring them up and that match the lights already on the rig.
Anything to increases the visibility of the rear end of the RV to followers in traffic. Was in Walmart the other day looking for something else and just happen to see them, cost $12 made by Bully. Is a LED brake light and tail light. We don't use the rear RV hitch for anything else so this works for us. Google them and you can find all kinds and styles of them.
Just some economical things to think about to add to your rig.

Steve