Interim: stack up 2-3 courses of concrete block leaving an fire door opening in one end. Place a cooking grate (rebar & any old grill grate), add 2-3 more courses of block. Get a chunk of tin or sheet metal for a roof & another for a door cover. Light a fire, add the meat, close her up with a final block holding the tin down and another for the door adjust the top & door for draft. I cooked butt, chicken & ribs like this for 15 years.
PS: Get LOTS of beer - you will be fire tending a lot more than with the WSM or UDS.
Got a bunch of cooking toys and a custom metal fabrication shop where I spend my time building all sorts of smokers & outdoor cooking gear.