Before buying mail order from any web site, check out the company's reliability at the web site www.resellerratings.com
(which has customer reviews and ratings). B&H (www.bhphotovideo.com
) in New York is a big-name place with most anything photography-related you could want, and is completely trustworthy with good customer service. They may not be quite the cheapest, but any place cheaper is probably much less trustworthy; there are a lot of scam-prone camera gear places out there. There are several other similar online places that people here on the forum have used, but B&H is probably the most popular and well-regarded of them.