Berthing in Hawaii is difficult with state run harbors on a 3 year wait list. There are tempoary slips but I think limitied to 30 days and you really need to have someone watch your boat as most harbors get a lot of swell action. One option is the private Kolina Marina on Oahu. They should have space but at around $1000 per month depending on your boat length.
Forgot to add that the recent Tsunami reduced the number of slips in hawaii by several hundred- increasing the demand even more for slips.