Another vote for building it yourself. It's not as hard as it looks and it is very satisfying cooking awesome BBQ in something you made.
Some suggestions for your first build:
Don't get fancy with your air intakes at the bottom of the barrel. Just drill the holes and use flexible magnets to control the air flow.
Find a used 22.5" Weber and use the lid for your drum. Your local scrap yard should have a good supply of 55 gal drums for sale with the tops cut out. Just take the Weber lid with you and test fit it on several drums to see which one fits the best.
Good luck and have fun!