I've heard good things about this product called Provent A Mite (people correct me if I'm wrong....isn't this one used by a lot of people??) It quickly kills mites.
http://lllreptile.com/store/catalog/...-and-cleaners/
You will not get rid of them just by cleaning out the enclosure, you will need a mite killer. Here is a youtube video by BHB on health issues, including mites. He tells you exactly how to use the mite killer.
http://www.youtube.com/watch?v=pJCnPfuqaBM
It is sad that a breeder would knowingly sell a bp with mites, they could have at least warned you before you brought him/her homehow sad and uncomfortable.