We toured Kona this year and frankly didn't see a flat that I could fish. But, there was a couple of places where a sinking line and a Clouser should work. The marina just east of the airport has some areas that looked good. You have to walk 1/2 mile or so. I suspect wet wading is best.
I looked at this guy
http://bonefishhawaii.com and decided that island jumping for a days fishing was a tad expensive.
Maybe another trip is needed!
Regards,
Don