Ebay is usually pretty helpful. I got my first egyptian beaded bra and belt for a pretty low price. Amazon has some good stuff as well, another dancer reccomended bellydancestore.biz. You might be able to find something here as well: http://www.dancedirectoryplus.com/Dance-Wear/
Your other best bet would be to find out about a belly dance store in your area, a dance store, or even some kind of belly dance swap meet. They will haggle with you for prices sometimes.
I hope that helps! Let me know if it all goes well. :)