Shapers Barrel left tightening nut

I finally got around to putting the Shapers Barrel from Australia in one of my Skil 100’s.  The original nut that holds the gear for the belt is too small.  The Shapers Barrel didn’t come with a nut.  Anybody ever run into this?  Any Idea where I can get a nut that fits?  Any help would be greatly appreciated.  What abrasive cutter heads for the Skil 100 are other people using and where did they get them?

I think that nut is reverse threaded. In other word to tighten it you turn counterclockwise.