goofing off, I tried a piece of paperboard (think baseball card) in the belt... it actually worked to make a buzzing noise. we all laughed about it, but I took it off before it got sucked into the sprocket.
maybe something similar, but not as crummy? im thinking flexible plastic like some flexible 3 ring binders have, and a couple zip ties.
unless you have spoked wheels... then do the wheels. lol