Dont ask for an invite, you might just embarass yourself... im kidding, but seriously, dont

http://left4deadforums.com/1669-deathtoll-deadair-maps-versus.html

They are unofficial as they were not released by Valve, but the maps are authentic, just not rebalanced for Versus.

As it explains, you can play these maps if someone else has them, I can host a server on my machine alright, id have to test it out but a couple of my friends on the east coast connected well, so maybe we can get a good game going on these maps. Either way, i would suggest downloading them, as they dont replace or mess with anything, just add another 75 odd mb onto your l4d.