I remember seeing that those are sold as two parts. Since the rebuild kit is the exact same as the Honda CR500, I believe you can just buy an OEM honda nut (which they sell separately). Someone with a little more knowledge/experience than I should be able to confirm this. The part number for that is 52438-KA3-731, it looks like a 12mm hex nut, not sure if that's the size of the one in your link you posted? If you wanted to completely rebuild your shock, the kit is 129994600801 (don't believe that comes with the nut). Best of luck!