You could look for an outfit that does slitting, but most of them will probably want to sell a coil. 16 ft. is longer than a shear can cut so most metal suppliers won't handle sheets that long.
If you are can get by with less than .030 get a roll of flashing from Lowes, HD. etc. You can cut it with a sharp case cutter.
Metal fabricators can help you. My brother has had custom aluminum pieces cut for his 'party barge' and a few other maritime projects He said that is the best on price he could find too. Good luck!
I found a great fix, I went to a seamless raingutter supply company, they have a rolling shear allowing me to get a 16' piece without having to have a seam! The material is the correct thickness and is coated white. Since I am covering it with a blue stripe it works perfect, and was cheap to!
Thanks again!
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