Supercharger Idler pulley question?
 

I heard something this morning like I ran over something on the way to work. I just happened to look under the hood just now and the S-Belt was laying there and the outer most pulley was gone except for the torx bolt and part of the bearing. It is the outer(towards the front of the car) and upper most one. I looked at Rock Auto and got confused. I believe it is a ribbed pulley, not a smooth idler type.
Does anyone have the size or maybe a Gates number so I can call and get one locally. Cause no matter what I do, the local people will be wrong! Any help will be appreciated as always.
Thanks guys!!

I have one here, $15 shipped if you want it. Just send me a PM