I know what you are talking about but I can't think of the company that makes them. Go to
AgTalk Home - Category & forums listing and ask there as those guys would be more familiar with this item.
Mark, he is using the word caddy but think of it more as a dolly. It basically pulls the mower offset from the tractor so like he said, the tractor would stay level up on the road and the mower would be in the ditch. I will see if I can find any pictures or information on it.