In case you're not aware of it, your small propane tanks can, in a crunch, be refilled from the larger ones used for gas grilling. It's a hassle to do; but, as long as you can cool down your empty tank (refrigerator, cold running stream, well) to condense what fumes remain, you can get a worthwhile fill level. It just won't be as much as in a new tank. The small propane tanks are fairly inexpensive; so, it's not something you'd want to do regularly. Still, it wouldn't hurt to keep a coupler with your grill just in case you ever need to bum some gas off someone. The coupler is simple and doesn't cost much:
https://www.ebay.com/itm/MacCoupler-...AAAOSw9mFa-eCD