You could try Student Job Search.
I got babysitting jobs from there when I was childless!
At the moment, I have a deal going with a few of my mummy friends where we do babysitting exchanges. It is great as I feel so comfortable leaving Han with other mothers. The night-time outings are usually with my next door neighbour which is even more advantageous
If all else fails, I could do it for a special occassion until you get someone sorted - Despite not knowing me from a bar of soap! I'm on the other side of Wellington, so as a regular babysitter I wouldn't be suitable, but I know how much of a pain in the butt it is to be stuck at home with a baby