After seeing the original design I wanted to make versions for some different phones, unfortunately this wasn't possible with scaling alone so I decided to copy the design in OpenSCAD and make if fully parametric up to and including the design of the TOP and the embossed LOGO.

Adjust the Width and Depth variables to your smart phone dimensions.
If desired change out the two LOGO stl files (Don't forget to specify the dimensions).
Create (F6) and save the STL using OpenSCAD.
Slice & Print the STL file.
Clean up as needed and enjoy.