over several years i found almost all at Greenberg shows or on ebay, the last one just a couple of months ago. All of those that were only produced once by Lionel, including the green one, are hard to come by, especially the older ones produced around 2002-2005. Maybe the hardest one to find is the Saskatchewan Grain 17189 Brown/Orange one but i will give you a lead that there is one on ebay right now. This is one of my favorites of the group.
I wish this one would be produced in O scale (i posted this pic before in your CN thread)
joe