Just make sure it's got the N3 type plug, it's the same one for 20D, 30D, 40D and more. There's plenty available. Either the one Wayne mentions above, or many different types of 3rd party ones on eBay that work equally as well at a fraction of the cost. I have the Aputure brand one. It works flawlessly and thoroughly recommend it.
http://shop.ebay.com.au/i.html?_nkw=...1&_from=&_ipg=