SS drums are available, but expensive new ($600-$800) and rare used. I got lucky and found a few. They turn up on ebay, but the shipping will kill ya unless you're close by. I've built about 6 of these, and have tried various changes. The tough part is finding a lid, or making one fit. My lid is SS, made by a company called Arctic, that seems to have gone out of business. A Weber 22-1/2 lid sort of fits. I added a strip of SS around the inside of mine, and the lid fits good. The whole theory to these smokers is that they be air tight except for planned vents. If the lid leaks a lot, you won't be able to control the temperature. Here's some pics:
On this one, I used a huge SS bowl for a lid. When I cut the top out of the drum, I left a 1/4" ledge for it to sit on.
I use U-bolts to hold the grates up. Grates are from a 22-1/2" Weber. I made a drilling fixture to drill the holes for the U-bolts. Notice two sets of U-bolts.
I drill three holes about 3" up from the bottom, using a step drill. These each get a 3/4" pipe ******, held in with conduit lock nuts. Each ****** gets a pipe cap to close them off as needed.
I make the fire basket out of #9 expanded plate, and the bottom is a charcoal grate from a Weber 22-1/2". You can also make the bottom grate out of expanded plate. I bend a handle out of 5/16 steel rod. I also add three legs that line up with the U-bolts. That way, I can put the fire basket on the lower set of U-bolts when I want to do direct grilling. For smoking, the fire basket just sits in the bottom of the drum.
As I said, this lid is a SS 30 qt. bowl. I make up a handle, and I made these SS copies of a Weber smoke vent so you can shut it down when done. I should have made a bunch of them, as they are all used up now.
That's the 'Cliff Notes' of building a UDS. There's tons of stuff on-line of you search. Regular drums work just as well, especially if you can store it inside so it doesn't rust out. Find a used Weber grill on craigslist for the lid and grates. I have two cooking grates, and have used them both at the same time. When I smoke a turkey, I put a water pan on the lower grate and collect the drippings to make gravy. I smoke pork and beef at 225, which is one bottom vent open, and poultry at 350, which is two vents open.
