I just started looking myself. And I can tell you where they DON'T have maternity wear...Macy's at Ala Moana. I couldn't believe it. Not even ONE maternity bra. Craziness, I tell you.
Old Navy had some stuff. Cute? Kinda. Pricey, I'd say it was more expensive than I wanted to spend on something I won't wear after this year.
My husband also told me about The Hot Mama in Kaimuki http://www.thehotmama.com. Haven't checked them out yet tho.
You can also sign up for Zulily.com. They've got cute maternity clothes and things for baby for up to 60 off.
Hope this helps. And if you hear anything other places, let me know. :