Hi Guy, there are NO GT specific charter operations in all of Hawaii. Best bet would be to contact forum member Charlie Cintron on Oahu.
Again, there are no good tackle shops in Hawaii that carry GT gear. We have to buy almost everything online.
For GT related souvenirs you can definitely find plenty of good stuff though. When you are on Oahu, try and look up "Gyotaku by Naoki". He does some excellent fish printing work of GT's and other local fish, his stuff is a must see! You'll probably also be able to find some carvings of GT out of Koa wood, and also many styles of fish hooks carved from bone, shell, and wood.
THis time of year is typically our "off season" for GT fishing. The shoreline fishing can be extremely poor for GT's right now, but Charlie will be able to find plenty of bites from the boat if he is available. You can also contact Nervous Waters Flyfishing and try for a shot at some MONSTER bonefish on the flats!