Hope you find what you need. I noticed that kmjFarms posted a link on the previous thread.  Here it is in case you missed it.  http://www.amitytech.com/tramlines  This may be the same company because they use the name "Air Tram."  I had the Tram-Rite on an older JD 750 years ago and have used the Air Tram the past several years and never had either one malfunction in any way.

 P.S.  I ran about 160 acres this morning before it got too sticky in the tramlines, but they were easy to see even with 1+ inches of snow overnight.