I had these sort of rain channels on my first coupe as well. The previous owner must have made them himself. It's a simple DIY job with a few strips of aluminium cut and bent to shape and a few small screws or pop rivets.
I think if you are looking for this type of channel or gutter, you need to be thinking Land Rover. This I believe is a standard item on Land Rovers. But why a gutter, that just creates drag and doesn't look as clean. You would also have to consider painting the gutter! My Vectra has rubber moulding which fits between the top of the door and the door frame. It's difficult to explain what they look like, so you need to look at modern cars. The Audi TT is another example, but I don't know how it works! But there must be more modern ways of skinning the cat!