Long story short, I don't think you'll find it or a similar product in 12'. Dibond, Alupanel, Polymetal from NUDO... 5'x10' is as big as they go. I believe you can get
Alucobond in 12' but it's really pricey, better product but pricey. As far as dealers? Start calling suppliers, our in St. Louis will find it for us if they don't have it. Good luck