I thought I had found one online.... we want to experience a sleeper train on the way back to Prague from Salzburg.
The Zürich-Prague night train stops in Salzburg, but not at a great time. It departs 3.50 so I would personally choose another train.
MyDayTrip.com has private car transfers on that route. It takes 4 hours and rates start at 55 euros each.
Sure would be a much more pleasant than a train.
Thanks for the response.