sourcing

I've been lurking for a while but reluctant to post for a while, but I've finally reached a wall and kind of need some help in regards to lights. I have never diy'ed a light before but have built a PC and have googled and tried to find the answer to my questions before coming here. Please...

One of the only products I'm having trouble trying to source is the 18AWG solid core copper wire, any other Australians here able to find any domestically without having to go international?

Specifically referring to bigger/budget brands. Fox Farm, Cutting Edge come to mind. Where do these brands get their nutrients from to include in their liquid fertilizer? Specifically, where do they actually "source" their nitrogen to put into their liquid blends? Does it come straight from an...