This labyrinth is said to be found in the middle of the Ko'olau Caldera on the windward side of Oahu. I've never been but the location looks interesting.
This one is found at the Dragon's Teeth point of Kapalua, Maui. (If my memory serves right, you can just pull over to the side of the road as you drive along the island's ridge.)
And of course there's the world's largest maze at the Dole Plantation on Oahu. (This one is more a tourist activity than a prayer labyrinth.) There's a fee for the maze enterence; if you're up for pineapple ice cream scout for some tourist coupons and grab a 'Dole Whip.'
There are additional labyrinths on Oahu, Maui and the Big Island including a small one painted onto the UH sidewalk. For more info see: