I use Landwatch.com for all my land searches in OK. You can filter your search fairly well and get down to the minimum acreage, by county, etc.
Tell me if you don't mind: Your budget (approximate) and what are your top 4 counties you'd prefer to own this shooting land in. Do you hunt as well?
No budget in mind, though less is more of course. No preference on counties either, I will go wherever the best deal can be had. I don’t plan on doing any hunting, just poking holes in paper.