There really is only one surefire way to get this right, and that is to watch some films made in the 1920s which were set in the (then) present day.
It doesn't matter if they're silent films, because you're looking at the fashions!
Try Hitchcock's first (sound) thriller Blackmail for instance, or any of Laurel and Hardy's earlier films.
For "glamorous" fashion, this is more difficult, because this tends to feature in musicals but there were a few made at the very end of the 1920s; search film encyclopaedias for details. (or the Internet Movie Database!)