Those are difficult units to find, from my limited research.
I was actually interested in the dometic/seitz products because I thought the design looked cool and progressive/aesthetically pleasing. But researched them enough to find out that the cost was high and the availability low. Also a lot of mixed reports about plastic bits breaking and skylights flying open unexpcetedly... although these are second hand reports (hearsay).
Good luck in your search, I mean that. If you find a good US distributor come back here and post the info. I still like the design for some reason.