Hey Jono,
Great choice of game!
I am also in NZ.
I am lucky enough to have an original USA Robotron which is also my fav game.
There was a thread a while ago about someone wanting some plans. Did they get any?
Moon Patrol and Joust are pretty close. Couple of differences on the sides are that Robotron doesn't step in below the CP and the angle cut above the CP isn't parallel to the CP itself.
Mine is going to get the full resto treatment soon so I can send you some pics if you want?
Good luck.