After reading over how other people have used yellow felt to create a yellow hat and realizing that I value my sanity too much to attempt it, I decided to go thrifting and find one to spray paint or dye instead. That didn't pan out so well.
But one trip to Michael's later, and voila! For $4, I scored a brown foam explorer hat! I already had yellow spray paint, black ribbon, and hot glue on hand.
If you're wondering how I made the faux necktie or how I changed the outfit from white to yellow, just follow the links :)