I think I have seen what you are talking about.  One of my crop consulting customers had these on this planter last spring.  He is no-till-chops the stalks at ground level then plants right down the old row.  He was tired of his rubber tires wearing very quickly.  From what I saw and remember they worked very well, especially given the tough condtions of last spring.  As I recall he said he got them at the local Deere dealer (In York, NE)

Hope this helps

Ryan