PINKBAOBAO, I was just in Waikiki. You just need to go in everyday (sometimes twice a day like me LOL). They have good turnover/new inventory everyday. I have been to Waikiki H MANY times, and there are birkins almost everyday.
If you are not picky about leather, hardware or size... you will surely score a birkin.
Please see the Inventory Thread for the Birkins spotted at Waikiki H last week. Good luck!