My guess is that this green coat was either a std. production item (i.e. actually in some companies product line) or specially made for the movie. Usually for an item like this that appears in many different scenes it is necessary to have several backups for it (also ones to fit the doubles). It's just too risky, if something happens to the one piece you'd have suspend shooting the film ($$$$!!) until a new one was made or reshoot (again $$$$). Obviously for the jeans, shirts and hats this is not much of a problem, and the Carhartt coat was easily duplicated all being ready wear items. Even Jack's black truck had a back-up for certain scenes. This would make a really interesting research project to try and find out the story here with this coat, if anyone knows anyone connected with the wardrobe dept on BBM it would be a place to start.
I have recently been trying to do some research on Ennis's first hat. It was labeled as a Stetson in one of the auctions, but I cannot find a truely identical hat in their line. There is a very similar one, but it has a much shorter 4" crown. Ennis's hat is very tall when compared to other standard cowboy hats, looks like a 6" crown. I'm wondering again if this wasn't custom made, designed especially look good on Heath's head? It sure does IMHO. If anyone knows any details about this hat I'd appreciate hearing about it.