Rather it be the earlier Green model, or the 1980s Centurion Mark II model, are rarer than crab teeth! One lucky vacuumlander found a BRAND NEW Centurion Mark II some time ago!
Bisons were made in Ocala, Florida, not far from Jacksonville! The company was started by a former Kirby worker who believed he could build a better machine (and in some ways he did!). Kirby's design was changed just enough to prevent suing (such as how the Sani-Emptor on the Bison opened from the side, and was called the 'Empty-o-Matic'!). There's legends about the distributor, too, but I won't go into those here!
But if memory serves, Jimmy Martin, aka rugsucker had a green one new in the box for sale.....I know he's busy cleaning out his warehouse but he might be able to dig it out if he still has it!
I still have the Centurian basically new in the box with the attachments I purchased from Fred. I used it one time and if there were ever a vacuum that should have been self propelled it should have been the Bison's. The machine is a beast to push around.
My Bison Centurian is strickly a show piece. I'll stick with my self propelled Kirby Sentria's for daily use.