Clearly, OS X Lion 10.7.x is no longer downloadable from Apple store.
Download Mac OS X Lion 10.7.5.DMG – Mac OS X Lion 10.7.5.ISO – OS X Lion 10.7.5 torrent – Retail DVD uploaded. Well OS X Lion is not available in the Mac App Store but you can direct download Mac OS X Lion from puter, This is an official App Store installer.