There's also the Olympus 9-18mm in a micro 4/3rds mount. I have that lens currently as I didn't want to spring for the 7-14's and a dome port. The 9-18mm worked with my Olympus housing's flat port, although it isn't ideal for getting the widest image possible. Corners aren't the sharpest, but for the money it's a good option. It's only a small step down in image quality compared to the Panasonic 7-14mm, for instance. New they are $400-500 USD here in the states, not sure what it is for you in NZ.
If you have the budget, by all means go for the Olympus 7-14mm PRO lens. That would be the absolute best lens in this focal length.