Well like someone said early go to electronic stores. Circuit City will be a good place because they will have slashed their prices and everything will be really cheap. Or go to your phone service's store. They will have everything you need. Finally, use Ebay. You can find ANYTHING you need on Ebay.
There isn't one that I recommend, but try electronic stores, or even stores that sell everything (including electronics) like Target, Walmart, Best Buy, Circuit City (even though it is closing.)