My trailer (195rb) also didn't have an outside jack, but I added one. As RoyBraddy shows, the inside power supply unit in my case did have an unused connection for an outside jack. I just connected my coax cable from my new outside jack to that connection. Now it works just like most trailers that come with an outside jack.
I do have to say this mod can be tricky because of what's inside the walls. In my case I only had 4" left and right of the inside power supply, 6" below it and lots of room above it. So, if you attempt this, be sure to remove your wall mounted power supply and probe all around it inside the wall. It could be very disappointing to drill a 1" hole in your outside wall only to find you can't get a coax from there to your power supply.