I put the tank in the truck in a milk crate. Usually try to find a local Tractor Supply on the smarter than me phone as they charge by the gallon only. If not, a regular LP place. For a motorhome I used to have to find a LP dealer where I could pull the motorhome up to for filling. Flying J used to have LP. Some parks have a LP turck which comes through certain days and you have to sign up for it.
Lots of options. Also, my understanding from an LP dealer is the exchange tanks are not filled to the normal capacity and be careful in getting one with an expired OPD.