Assuming you don't want to move to fill, or have a LPG supplier visit frequently, what you have to do is feed from an external tank. This is best done with a T-fitting between your gas valve and regulator, which a LPG supplier can install or you can get DIY solutions like extend-a-stay.
To fill from an external tank, you would need an external tank that supplies liquid. I think modern DOT bottles are specifically designed not to do that, it is one of the functions of the OPD.
If you are going to be there long term, and can get a local supplier in, you can usually rent a larger external tank. This can then be filled as needed, less often than small bottles.
If you want to do it with portable bottles, the exchange bottles are the most expensive way to do it. Price for the convenience is often double the price of the gas provided. Having your own DOT bottles is almost always cheaper, unless you run into "minimum" charges or service charges. Handling larger DOT bottles (30, 40 and 100 pound bottles) can reduce the impact of service fees, but it is a matter of what can you handle, i.e. those three are 24, 29 and 68 pounds empty, respectively.
The rental alternative, most likely a residential tank, requires sizing the tank to the consumption. A LPG dealer doing rentals can help with this. I see tanks in the 200-400 pound range trailer parks, where the practice might be one or two fills a season.
Tom Test
Itasca Spirit 29B
