Not sure. You can use the Stacker barrel section, but that gets you close to $200, not much better than a new wsm. If I can locate the right size pot on the cheap, well that's another story. Can't have too many weber smokers.
ECB should be about 16.5" diameter, my thought would be to cut it and add a 3"? piece to make it fit. A 30 gallon drum should be pretty close to the right size.
I am assuming the size compares to the little kettle. I just tried to place my NIB Stacker (don't ask my wife why I have had it for a year and it is still unused in the box) on my 18.5 kettle and it doesn't work right side up because the lip structure is made to fit inside the WSM's section like the lid does. I suppose you can mount it upside down and change around the hardware but that would be a major pain. JMHO.
Love my mini! Always gets lots of comments and questions at comps from people that have never seen one. I'm thinking about building 2 more to give as Christmas gifts.
a store i went to has it listed as $60 . but yea, you can buy a used wsm cheaper on cl than try to make something out of this. unless you are a sheetmetal worker or are handy enough to make yer own barrel.