I have a Mac Mini running OS X 10.6.8. I wish to install Xcode 5, which requires 10.8.4 or later. My machine is not powerful to download the free upgrade to OS X Mavericks via App Store. I would like to upgrade my machine to 10.8.4 via App Store but when I search for either "OS X 10.8.4" or "mountain lion" there are no matches. Is there a way to obtain Mountain Lion?