These super-cool metal bands come in all different sizes and range in price from $5 to hundreds. You can buy them at H&M for low prices.
I'm not really sure where one could buy this. However, a DIY would be pretty simple. Just glue spikes from the art store to a leather ponytail band or a metal hair cuff. You'll look instantly edgy.
Tousled, textured, voluminous ponytails look perfect with a big, fancy-pants bow. These are even cuter with a sheer, chiffon bow. H&M also sells these.