Good luck finding anything Sportbike related there. The islands are all about Harleys. Sportbikes are just starting to make inroads there, and those riders get hasseled all the time by riders from the "Dark Side". Also, no helmet law - very weird to see someone flying down the highway with shorts, tank top, slippers (flip-flops), sunglasses, and no helmet

- but that's how they do over there.
There is a shop at the Pearlridge Mall called Razor Racing Shop. They cater to road race cars but do have some helmets (mostly gaudy Suomy stuff) and some jackets, but you'll be sorely disappointed at the selection if you make the trip out there from Honolulu.