Not much to choose from on those islands. The big island will only have sport fishing charters in Kona and Maui's west side has one beach cat rental, I think the guy's name is Chuck Johnson. There's some big cat "cattle boats" that sail on the west side of Maui also.
I almost forgot! there's a guy in Kona that just bought a used Hobie 17, his name is Art McMahon.
Hope this helps