Not sure about hiring gear, there are a couple of local schools you could ask.
However Air Calin has a free 10kg allowance for sporting gear including kitesurfing, so easy to bring your own!
Just make sure your flight is not an Air Calin operated by Quantas cause you'll have the quantas allowance as I experienced recently 
New Cal has some amazing spots, enjoy!
I was there last April.
There's a lot of kite schools with trailers full of gear for hire all along Noumea seafront. I advise you to take your kite & harness on the plane and rent only the board as it is quite dear to rent (that's what I did).
Careful, the tide goes down pretty quick over there ;-)
