Like CatMonster said, the hat I ended up using for my Luffy costume was found at Michaels, many many years ago. (I'm Charli, by the way. I'm a LURKER XD). It has worked wonderfully for me, through many abuses and moves, and still looks great.
I'm looking at redoing some of my Calgara costume, and finally getting around to cosplaying Eneru in the future~ Been re-watching One Piece with my girlfriend and we're smack in the middle of Skypiea. (I'll finally catch up too, heh.)