That's an excellent question and it makes me think of a few solutions for you:

• avoid ever buying any OTA gear at an RV store - their price markups are enormous!
• a UFO-style omnidirectional antenna can do very well on an RV but they're a bit pricey even from regular OTA sources - good thing is that they can be permanently mounted to the RV's rooftop
• a medium to small sized VHF/UHF combo can be taken along with a telescoping mast, but you need to frequently lube the folding joints and always wrap it before driving anywhere if it stays on the roof during travel - I see antennas like the Delhi Zip models being used for this
• there is a collapsible, flexible model of the Gray-Hoverman antenna that you can build

I've moved your post into this thread that discusses other RV OTA gear.