Thought I would share this adapter since it took me awhile to find such a thing. It's kind of the opposite of adapters that let you hook a grill to a big tank. It will allow you to attach a small 1lb propane cylinder to your trailer in an emergency.
Anyone who has a trailer with a single 20lb tank is familiar with running out of propane in the middle of the night. After you stop laughing... a 16oz cylinder should get you thru the rest of the night or finish cooking dinner. Google "Amazon B071ZHQVL3 propane adapter".