A leather hair tie, like the one I wore to this years Renaissance Faire, fit right it. It's just the kind of crafty thing sold in many of the fine shops but I was fortunate enough to spend way less on mine at a weird tourist trap called the Tepee in Cooperstown.
Though it's traditionally more native American than anything to do with the Middle Ages, you'll find that when you go to the Faire, there's a hodge podge of various eras and ideas that are acceptable to wear and often some things that should be out of place (like maybe fur pants, devil horns, and angel wings) are actually perfect.
And I might even wear this accessory in my daily life too…
But what do you think?