Yes, there is a kit call add-a-tank that can be installed on a class A or C to allow connection to an external propane supply. They are seen often in extended stay situations where it is not feasable to move the rv to a fill station every few days in a winter cold location. And most propane or gas dealers will bring a larger tank to your location and install it for a monthly rental fee and the price of the gas. Usually there is a minimum time period involved also. Many full-timers have them installed, and if needed, they can just go to the local walmart and get a portable tank to hook to it.