As soon as I have the final dimensions, I will update this one:
The .scad file is compiled by OpenSCAD to generate an .stl file. The model will work for silicone or any rubber-like material. A one-off at 3D hubs runs ~$70, but the price drops considerably with a volume order. Purism employees have communicated with me about this, but I am not aware of any plans to commercialize it by Purism.