You know how the gas always runs out when you're in the middle of cooking as opposed to right at the start or right at the end? I went down to the local servo where they have the 'Swap and Go' bottles. They are $24 if you bring down an empty, but $90 if you have no bottle to swap. I wasn't going to pay that, so I went for a quick drive around some of the local back lanes where people often dump stuff. In the third lane I found a very old, rusty gas bottle that somebody had tossed out. I grabbed it and swapped it for a $24 full bottle.