Suntour offered the Superbe and Superbe Pro rear track hubs in 40 hole drilling for tandems. You can't get a better hub from any era, by any manufacturer (my opinion).
Aside from those, there are certainly other 40 hole rear hubs available, again the more modern ones would have been for track tandem use and older would have been for the classic 32h front, 40h rear lacing of British bikes. The single piece hub you're looking for would be a BH Racelite, the Airlites are 3 piece.
Phil