These two blasters, recently shown by Wired, seem to be built on the Bergmann 1896 automatic pistol:
Note the very distinctive grip, trigger area, and slits in the magazine cover:
And yet, the outline of the magazine cover doesn’t quite match. It’s possible that the bases for these blasters were simply inspired by the Bergmann, and built from scratch in 3D and then 3D printed. I do not know of any replica Bergmanns available. Additionally, the Bergmann only has the magazine cover and slits on the one side, the other side is solid; and when I first saw these photos, they were facing the other direction. I flipped them, assuming them to have been reversed by accident, but if they were correct originally, it lends more credence to the inspired by but scratch-built theory.