Based on Thing #78071 this adapter suits a wide range of tested phones including the super fat HTC One M8 but most importantly the iPhone. The original .stl files were edited in Blender. The holes are now 4mm diameter (suitable for metric m4 fasteners).
Print out the .stl files (you will need 3x Side holder).
You will need:
2x 80mm m4 fasteners
2x m4 wingnuts
3x 30mm m4 fasteners
3x m4 nuts
To see my Thing in action check out https://www.youtube.com/watch?v=m730oYo-v3Y