EDIT: Oops... sorry... my note below only works if you're departing on a *A flight.

Try this handy lounge locator tool on the united.com web site.

With respect to *A lounges, you can use the NZ Koru Lounge, SQ Krisflyer Lounge and the contract lounge. Not sure what the contract lounge is though... I've never been. I prefer the SQ lounge over the NZ lounge.