Do
not spend any time learning about the different part numbers involved. Sure...you can, but you don't need to.
You go to CollegeHillsHonda's website (I think someone already provided the link), you look for their Si Rear Sway Bar kit (when I bought mine it was probably $65 + $18 shipping), and
everything let me say it again in case I wasn't clear...
every bracket and tool and nut and bolt and bushing and everything you need is included in the kit. 