Sayersbrook Bison Ranch is a real working bison ranch in the Ozarks. I'm not sure how many miles of trails they have, but it's a quite a bit. The trails are not open to the public like RORP, but are available during special events. There will be guides for all of the groups.
The Ranch is in Potosi, MO. That's about an hour and a half from St. Louis, but it's closer to three hours from Rockport.
Nothing against Rockport, that place is great and the folks that run it are really nice people, but the Ranch is kind of unique wheeling experience.