Mrs. Dog and I will be driving down the road in an 03 Suzuki Vitara with our teardrop following along behind. The Vitara has rear lights that look like this:

We are wanting to be reasonably retro with lights that look like these:

My question is: how do you make the lights work? We are going from three on the car: amber turn signal on top with red running/stop light below to two lights on the trailer. What happens when you have your foot on the brake while signaling a turn?
I'm sure this is not the first time this particular wheel has been invented so make me feel humble by telling me the simple answer.
Thanks for the help Teardrop Braintrust!