It can be found here: http://www.adobe.com/support/flex/downloads_updaters.html
It's not clear to me whether the updater updates Flex Charting and Flex Data Services. The page says: "The 2.0.1 updates for these Flex products can be implemented by installing the full, updated versions of the products." So I don't know whether you have to install the product from scratch if you are using Flex Charting and Flex Data Services.
