Sorry for the delay re my white dinner jacket.
About 25 years ago, I was cast as the leading man in 'South Pacific'. The costumer said I needed to wear a dinner jacket for a few scenes, and said they would reimburse me if I could find a well fitting one.
I lived in the Boston area at the time and went to a high end second-hand store in Cambridge, Ma and found one that felt (and still does) like wearing butter. If I recall it was ...$20. And it still looks and feels wonderful. ... Just looked for a label, and there was none. So it may have been custom made.
So, I'm so sorry, fellow Seabourn cruiser, that I could be of no help!
Peter