I saw the Gay Divorcee several years ago, before I knew much about concertinas, but the fellow (Tonettie) does play it in the film. I think it was an Anglo.
There's also nice concertina playing in Twelfth Night (96). Ben Kingley as Feste plays the concertina, since they reset the play in the nineteenth century. You don't actually see his fingers, so I assume someone did the playing for him.
Jim M