I have uncovered a cheat that I don't think anyone else has found to date. I have searched everywhere online, and even the official cheat document by Jason Emery that comes with the GOG version of the game.
You can get the Nort-Ship Z within the Full Game mode. No save game hacking or anything required.
The key combination clashes with the "Skip/Complete Level" cheat so you need to enter the keys in a particular order.
When in-game, press the following keys all together. F2 F4 F6 F7 F9 Backslash (\) Forward Slash (/)
You have to make sure to press F2, F6, or F7 LAST or the cheat will not work.
I don't think this cheat was ever intended to stay in the game and was probably for development/testing purposes because you'll notice that the Ship icon/animation in the Upgrade/Shop Menu doesn't display correctly.