This project is a bit more nuts-and-boltsy, but not too difficult. Take a few plastic barrels (you can get plastic barrels from your local food warehouse that might pack olives or veggie oil). Wash them, trim them to whatever size you want and mount legs to the bottoms (or not- they still sound interesting). You could also mount them permanently in the ground or bolt them to a fence. Or you could build a wooden stage and attach them as a permanent feature. BOOM! BOOM!