Below is the link to the Wyoming BLM to get maps and if you go through the website you'll see the unit locations and what maps cover it. Depending on the unit it sometimes takes 3 or 4 maps, but they're only $4 each. Make sure if you go out there that you have a GPS with landownership chip in it and it's imperative to know what roads are public all the way through so you don't get a trespassing ticket. The GPS/Chip doesn't give you that information, but you should be able to get a county map that shows all the publically maintained roads by calling the appropriate county seat.
http://www.blm.gov/wy/st/en/resources/public_room.html