Larnok
Play through three intense missions about the planet Larnok in the galaxy of Vidarnaq. This is the original campaign with a fixed download link, included AIN files. Fully compatible with the original VPK, what means that you can connect to each other or to dedicated servers with no problems.
Download
http://gamebanana.com/maps/190285
http://www.moddb.com/games/alien-swarm/addons/larnok
Installation Instructions