If you still have your Arkham City (PC) GFWL key (look in regedit under HKEY_CURRENT_USER\Software\Valve\TestApp57400\SteamKey), I've got the 4 pre-patch files you need in a 7-zip file in my Dropbox.
Just sign up for a Dropbox account if you don't have one:
https://db.tt/zgV0Mm0Then send me a PM, and I'll share the link. You'll have to put Steam in offline mode, but I can confirm it works. Just finished the vanilla game this morning.