This has been discussed here before. Please have a look at this related forum post:
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You will also find links there to some recommended suppliers of this product.
Electronics is a very competitive market specially if you are thinking of selling on eBay where wholesalers sell direct to the public. To compete in selling electronics, you would need to buy in HUGE quantities or source through liquidators. You will find that selling accessories is more profitable. Have a read through the forum post above and you will get a better idea on this.
All the best,