Can't really help with your question, but I did once find someone in Auckland that makes all manner of kettle/hot water/oven elements like you describe.
I bring it up because I was surprised there was money in it. If it's a viable business in Auckland, you might also find someone local.
Can't remember the name of them now, they were out in Penrose somewhere near Serious Shooters. Cool guys. Gave me a tour of the workshop and explained how they're made and everything.