Hi,
I know for certain that Audio Modeling is working on a harmonica SWAM instrument - this could be game changer when it comes to realistic harmonica sounds for the DM48(X).
In the meantime, there’s nothing really good out there to my knowledge - ThumbJam has a blues harmonica that might do just for silent practicing. There is the Chris Hein Chromatic Harmonica, but it is very expensive as you need to buy the plugin plus a full version of the Kontakt sampler - and does not run on iOS. It’s demonstrated with the DM48 in this very old demo video:
https://youtu.be/3ZpAqeLyiIs
I would wait for SWAM.
PS. My Yamaha CP73 stage piano has a rather good and realistic chromatic harmonica actually, but this is not a practical solution!