A simple design, uses two sets of materials: Flexible (TPU) and hard plastic (PLA, ABS, PETG, Nylon, PolyCarbonate, etc).
Here is a quick intro to the design:
In order to 3D print this design you will need:
A Velcro Band no wider than 1 inch:
https://www.amazon.com/VELCRO-Brand-Purpose-Straps-Strap/dp/B000TGX0HK?th=1
Loctite super glue control:
http://www.amazon.com/Loctite-1363589-Control-Adhesive-Bottle/dp/B003TP2TBQ
STL Download Link:
https://www.dropbox.com/sh/gfozkukfkbhhnpt/AAA8GOs2MGc7MOzs1kn-1ntra?dl=0