Several years ago I asked about that type of winch at an industrial supply shop in Port Alberni. I don't recall the details. I think they had them, or at least could order them, but the prices were a lot more than I was interested in.
I get the impression they are better known in the UK, Europe and Australia, than in the US. The best known brand in the UK is Tirfor. Black Rat seems to be the only one marketted to American drivers. I have also found references to this kind of winch among amateur radio people, since they are useful in raising towers.
paulj