I wanted a way to mount an exteral mic to my phone for mobile recording. Maybe this already exists, but I couldn't find it. So I remixed it.
Editing was basically on the vertex manipulation Blender.
After printing, you'll need to get 2 small screws, (you may need to drill out the holes) and screw them into the back to give the rubber band something to hold on to. Then, string a rubber band around the screws to make the phone holder grip your phone.
You will also need a 1/4" nut, 1/8" thick, and slot it into the hole at the base of the bottom. You may need to jimmy it in there good, but it should fit. and it won't need glue to stay in there.