I'd guess it's probably brown and silver yarn knit together to give it that look. You can always try searching stuff like prada, dolce and gabbana, and all those other unnecessarily expensive brands. You might be able to track down something similar.
So still have not had much luck finding this hat, I was just watching the movie again and noticed that the hat has a jolly roger scull on it! Renewing my interest in getting ahold of this hat or something close