I'm the guy on FilmJackets that identified them lol. Yeah they're extremely hard to find, I've NEVER seen one for sale online anywhere unfortunately.
Yeah the jackets are a b*tch to find. I've known the brand for about 3 years and I've never once seen one for sale. Dean also wears a couple Windriver button up shirts that I have too. I think the reason the jackets are so rare is because as far as I know, Marks Work Warehouse is the only place that sells the WindRiver brand, and the jackets were only available for one season. I'm kind of regretting not offering to buy the one of the guy I saw wearing it haha.
As for the boots in Season 1, I'm 98% positive they are Cat boots, not the ones he wore in Dead in the Water, but the all black steel toed ones.
I'm not sure about all of his Carhartt shirts but he wore an unlined version of the Carhartt S96, the Carhartt S111, he wore a Carhartt S113 a lot in the earlier Seasons.
Hope that helps, I have a whole list of all the different jackets and shirts and accesories I've identified lol.