How to get App Store back once it was deleted

Hi there,

I deleted the App Store application with App Cleaner because I was thinking I don't need it. It is also deleted in the trash. Without App Store I cannot download the OS X Lion, and even if I would search in former updates to find the App Store.app I do not really know what files I have to restore too to get the program working. There is no link at apple.com where one can download the App Store nor does the Software update offer an option to re-install it. Is there any easy way to get either a .dmg file to re.install the app and its related files or can someone give me a list of the files I have to restore from my updates to run the App Store properly, or any hint how I could solve this problem?

Is the OS X Lion also available from Shops who sell it?

Thanks a lot for your input!