If I didn't state it on the Bonne brooch tutorial, then I'll say it now; I am a cosplayer, and proud of it. :3
Now, one of my cosplays that are nearly complete is of Lan Hikari, who's like 10-11 years old and saves the world on what could be a bi/tri-monthly basis. /shrugs/ Not only that, he saves it with the aid of his trusty NetNavi/best friend/kinda-dead twin brother Megaman. (Yeah, don't ask.)
One of Lan's most recognizable features, aside from the fact that he looks like his dad, is his headband, which I managed to remake using materials I had on hand. :3 And what else did I do but make a tutorial on how to make it! /lolwut/
First, gather your stuff together, which would be:
~ One rectangular piece of blue fabric, stretchy or not (it doesn't matter), wide enough to fit the Hikari clan symbol on and long enough to go around your head and still have some left at the end
~ Yellow, black and red fabric for the clan symbol, each cut into one circle as wide as your blue fabric piece, one a tad bit smaller than that, and two pieces forming the red in the symbol
~ Thread matching the colors of all pieces of the fabric
~ Anything needed to make this easier, like pins, a pencil, something to trace a circle out with.
(This is what Lan's headband looks like 99% of the time in the anime. And yes, the picture looks weird right now, but I think it gets better if you click on it.)
Now, judge out how big you want your fabric pieces to be and get them cut out. To make it easier, make them bigger than they're supposed to be so that you can cut them down to a better size. Also, sometime the symbol is either smaller than the headband's width (where it's as big as Lan's forehead) or exactly at the same width, so judge whether you want it equal or not.) At this time, you can also prep your base fabric for the headband so that you won't have to work on it later.
(I have no picture of the base headband, but it's easy to understand I hope.)
Once your pieces are in the correct sizes, sew together your red, black and yellow pieces to make the symbol. Your symbol should come out looking like the pic. Don't go about sewing it to the headband yet, because there's a little bit to be told about that.
Now we sew it to the headband. Pay attention to the way the symbol looks on the band in the pic, because it should look like the pic when the emblem's sewn on correctly.
Now, if you're using stretchy fabric, then I pray to god that you sew tightly enough that the emblem won't slide around/act wonky when you're wearing the headband, but loosely enough that the thread keeping the emblem on the headband doesn't snap. Otherwise, I think you'll be alright.
By now I think you should be finished. If you think there's anything you need to do to fix it up at this point, go right ahead. Otherwise, you're finished!
(This is a pic of me and my cat Theo, shortly after finishing my headband.)
((Also, I didn't flip my photo after I took it, so it looks like the symbol's backwards.))