Where can I buy Good, Cheap Cosplay wigs online?

Well, I really don't have much money, but I'd really like to put together a cosplay. I know someone who's willing to make the costume, but I need to buy a wig. I need one that's around 10-20$. I've looked on E-Bay and Amazon. The thrift stores nearby don't have cosplay wigs. I would like them to be pre-styled, or at least cut to fit a certain character. Not sure which character, so if they have a lot of choices that would be good.