B Feelgood

So I was changing my serpentine and superchager belt yesterday and noticed that I was able to move my idler pulley back and fourth. It has a fair amount of play or wobble. It is just the outside pulley that the supercharger belt runs around and it circled in red in the picture below. Am I able to replace just the outside pulley circled below instead of the whole dual pulley setup that includes the serpentine belt? I found a few on eBay that seem to be the correct part. This would be much easier on the wallet instead of spending $400+ on the OEM dual pulley setup.

http://www.ebay.com/itm/Gates-38082-...item27c61ea6c7

http://www.ebay.com/itm/Goodyear-A-C...item4d004355f4

http://www.ebay.com/itm/ACDelco-3808...item2a1b7b1e4e