Damn! That sucks.. Do you have a spare casing or welding shop near by? I can't really recommend any other solution apart from JB weld maybe? We don't have it here in the UK so I don't know if that would do the job or not.
That's where someone tried to take the N sensor out with an open ended wrench and busted the case. I would order a used clutch cover off ebay and replace. They are usually like $25 shipped and you wont get a welded to fix it for less than that.