Actually it's not hard - you can get contact details for wholesalers in yellow pages.
Problem is that people don't want to go to official distributors & wholesalers because their pricing won't be attractive to sell online - at least for electronics, clothing, DVDs and stuff like that. Also, many of them are not registered as businesses hence official wholesalers won't deal with them.
So they start searching for a Secret Agent in China who will supply products they need for half price.