The only one I have ever seen was a shop-made outfit for hauling a JD 237 picker. The farmer that I purchased one of these pickers from (back in about 1984) had this cart and he let me borrow it to haul the gathering unit home (about 50 miles). It worked pretty slick! He said he had bought it from a dealer years before and it sounded like many dealers had carts like this for delivering new pickers out in the country. I don't know if Deere had plans available for building one of these or if someone at a dealership just sat down and figured out how to build one. I'm planning on building one this winter to haul my New Idea 319 gathering unit around.  I have a transport truck from a JD 350 elevator I junked out several years ago and I'm going to try to cut it down to fit this application (it's too wide right now). When I get it done I'll try to get some pictures posted.