Paul, Microsoft never has never let anyone just purchase one individual item from their Office suite of apps in quite awhile. If you really have to have the Outlook client, you will have to purchase on of their Office 2010 suites. Here are some options -->
http://office.microsoft.com/en-us/bu...102753654.aspx
If you do some googling, you may be able to find the home edition under $100. You do not have to purchase it from Microsoft directly, they are just offering you a quick download version of it.