I don't really know if they have the original maps at this site, but you can try, and you can get other user created maps here as well. Go to halomaps.org
After you downloaded it, open the folder, cut/copy the .map file and paste it into the Halo CE maps folder.
Start> My Computer> Local Disc (C:)> Program Files> Microsoft Games> Halo Custom Edition(CE)> maps> paste