Spreader bar with a large hoochie and chunk of bait works great most places. I'd recommend the spreader bar with a lighter test break off leader of about 6inches to 1foot for the weight. The north Island is pretty snaggy and better to lose only the weight, rather than a bunch of pricey lures.
Rock cod may be closed but there are lots of great eating species of fish up there. Learn to identify Cabezon, Sablefish, and Pacific Cod. Not sure if Lingcod are open up North right now, lots of good size great eating ling up that way. Sablefish are great smoked, and the others are excellent eating and a great replacement for Rock Cod.
Learn to identify Arrowtooth Flounder as well, they look like Hali, but have sharp protruding teeth. They can get a good size up there, keep one and try it. If you are going to eat one you must bleed, gut, and ice it immediately. They must be cleaned and eaten as soon as possible after catching. Don't bother keeping one if you don't plan on eating it for dinner that night at the latest. They have an enzyme that will make the meat mushy if not cleaned, iced, and eaten ASAP. IF you follow those procedures you will probably enjoy Arrowtooth Flounder for dinner.
I have only eaten 4 or 5 from the north Island, and found them quite good when cared for properly and eaten right away. Lots of guys will tell you they are trash fish, but they may not have processed it properly and eaten it promptly. Don't bother keeping them to freeze, they will be worthless if frozen. Try one before you right them off, you should catch some up that way.
Lot's of people throw back Cabezon because they have no idea what they are, and they are so damn ugly. Don't chuck them back they're great eats. There are lots of other bottom fish species up there you can keep. I love to bring back the Sablefish and Pacific Cod, they're fairly plentiful up there.
Have fun, and good luck.