I will assume you have the wireless Genie and mini Genies for second TVs?
If so you cannot have another box on your account. Sooo, you will need to take the Genie, video bridge, and a mini genie for your other TVs. To that you will need to wire your RV with new coax from a convenient outside location to the main TV location. Then it will only be necessary to buy an outside antenna. That can take the form of a tripod dish assembly for around 200 dollars, or an automatic rooftop antenna for around 1500 dollars. The rooftop can be very limited because of trees, whereas the ground antenna can be hard to setup. There is no dome type antenna that I know of that can be used with the Genie system.