Of course, if you call earlier in the year there are a lot of ranchers that are available to let you hunt on their land for a trespass fee. But you probably already know this.
Are there no leases available, or no leases available for the first few days of the season? What about leasing some land during the third week of the season? The common wisdom is that the pronghorn are easier to bag opening day and perhaps the bigger animals go down quickly after opening day . . . but unit 23 isn't known for big horns anyway and even in the third week of the season there are still plenty of pronghorn around and they are takeable with stalking and stealth, right?
By the way, what did the Wyoming biologists tell you was less than desirable about the BLM land in unit 23 -- such as the Thunder Basin National Grasslands? I'm curious because I have two permits for unit 23 and while I've got a two day lease, I've considered going to Thunder Basin National Grasslands as a back-up plan if my lease doesn't deliver in the two days I have to hunt it the third week of October.