As mentioned, The Wyoming DOW will send you a listing of ranches that charge trespass fees to hunt, I have the listing for the Gillette area, but it's a few years old, PM me if you want me to e-mail it to you. Just a word of advice, be prepared to make a LOT of phone calls, most of these ranches have hunters that return each year, and space is pretty limited.
There's a lot of antelope outfitters that have the private land locked up in NE Wyo. The areas I suggested aren't nearly as bad and LOTS of BLM land that is quite easily accessed. The Game and Fish will send the lists for that area as well.