Rich,
Try searching for waxed cotton--the more common term, at least here in the U.S.
One well known company that makes jackets is Barbour. The UK company Belstaff made waxed cotton motorcycle gear for years and still may.
Rivendell's Grant Peterson has been big on this for years and at various times has offered items made with it.
You can buy the wax, again, one source is Barbour (try Orvis stores), since to keep the cotton waterproof you have to re-wax it from time to time. So you could do your own.
Bob Schenker
Oakland, CA