Depending on the occassion, you can have something big and bold (and expensive!), like the ones displayed above, from Cherry Chau, Kyles and Basia Zarzycka.
Alternatively, most high street stores have more simple and affordable hair accessories. Check out these red hot numbers from Accessorize and John Lewis.
If you've got a creative streak in you, you can even make your own to perfectly match your outfit, get yourself a plain hair slide, or clip, and attach some ribbons, feathers, pearls, wire, beads...anything you want!