Then the Colorado Outfitters Association, and if not them, maybe Craig'sList or the local newspapers (everyone's online now anyway). I know I have heard of transferable tags before being offered in Craigs List.
Having said that, nearly any land of significant size is already outfitted. There is certainly a chance of finding something small(1,000 acres or less), but small parcels may not always reliably hold animals without crops or at least a major drainage. Because of the down economy, some outfitters may be overextended and underbooked, so I would think a sub lease to be the most likely bet for you.
There is one tip I have learned over the years in hunting whitetails in late season snow. Do not overlook soybeans left standing on the edges of fence rows, woods, creeks, buildings wherever it might be, this is where the deer will be while the food lasts during late season. December/January will pull deer in from some distance away to feed on the easy to get to food.
I killed one of my nicest bucks off of a very small patch of soybeans that was left after rains created a...