The truth is you can tour on any bike. It's just going to be a lot easier and hold together longer doing it on a name brand bike designed for loaded touring. One of the cheaper alternatives might be getting a Windsor Tourist form BikesDirect. You would have to assemble it, or pay your local bike shop to do it. You would also be taking a very big gamble on getting a bike that fit with no knowledge on what size you need.

I would suggest if there is anyway possible, to go ahead and pay the extra bucks to get a touring bike from your local bike shop and then you'll know it will fit. Something like a Surly Long hall trucker, Trek 520 or Jamis Aurora. Unlike a bike from Dick's they will retain there value so you could get most of the cost back by selling it after your trip, or will hold together if you continue to ride.