Very thorough online store that allowed me to lookup the Weber part no. that I needed and make sure it applied to my s/n. Thanks
Motor pulley (4 x 1/2) (vp) for: ada/asa
Motor pulley (4 x 1/2) (vp) for: ada/asa/aua51/5112/71/7112 & si500/50012
Buy this part and as many parts as you like and pay only $9.99 shipping, within the Contiguous United States.