Does anybody know good source of small pieces or offcuts of aluminium in Auckland area. I'm looking for 6061 and 7075 grade only.

I know Nalco but they don't have 7075. Is there any other good place. Also looking for brass and bronze.

Also interested in Sydney area as I'm flying there some sometimes soon.

Try phoning Ullrich Aluminium.
They have a factory in Wellington and you can rummage through their scrap. They may have the same in Auckland.
Model shops have small brass sheets and the like. Not sure about bigger stuff.
Paul

Ullrich Aluminium, Manakua Branch have both grades.
7075 cost, 1m x 2m x .25mm sheet is NZD$3500, will cut to any size... charge $50 per cut. I doubt they will give offcuts away?
If you find another source let me know as I'm after some large plates.