DIY Google’s version

The Google Cardboard viewers specifications are open source; this means that the instructions on how to build your own are free, and you can find them on this site: https://arvr.google.com/cardboard/manufacturers/ .

Google provides all the useful information for you to build your own viewer, such as material specifications, templates, lenses information and how to define the device’s parameters with the viewer profile generator.

All you need to do to build your own viewer is download Google’s specification package and read the information very thoroughly, you will find all the info you need, including rubber band specifications!