Make it or where to buy it? A steel supplier would be one place or any fab shop could order it for you but it's going to be the best price in a place that orders stainless in bulk and when I say bulk, I mean the rail car. I buy stainless from another fab shop here in my area rather than my steel supplier because they get it by rail load saving me about 20-40% that way.
I'm not even going to get into making it because I doubt anyone has the machinery to make it besides a steel plant. It has to be perforated, stretched, and rolled in the short explanation.