If you have an idea of the units, I'd call the the regional office assigned to that unit and try and get a hold of the bio assigned to that unit. They might know of some ranchers you can call about trespass fees. Also, try the game warden for that area, if they have been in that area for awhile they usually have an idea of some that might allow access for a fee. They also used to have a list of landowners they would email to you but not sure they still do that or update it. But its worth a try??
For the area I hunt for a buck what I'm seeing for trespass is a low of $500 but most are in the $700-$1000 range. Some will then allow you to shoot a doe also or some change $100 bucks for each doe, all depends.
You might also try contacting HuntNation I think it is, never used them so have no idea about their level of service but did email them about a hunt a few years ago - they offered some trespass only hunts on a couple of pretty big ranches around Gillette I think it was. The fee seemed OK from what I have seen.
But you better get on it soon, the better ranches usually have a big number of repeat hunters if they are any good so getting on a place this year might be tough but who knows unless you try - good luck to you.