I use my no-sew backpack strap to attach a PlayStation 4 DualShock 4 controller to my smallest laptop bag.  This has mostly been a good idea, but sometimes the strap keeps powering on the controller.  I don't know if this really drains the battery significantly, but it bothers me.  The “protector” doodad doesn't snap in or anything fancy.  I have mine held in place with a couple of tiny pieces of fun tack.

It is a pretty lazy design.  I imported a scanned model of a PS4 controller into OpenSCAD and diffed that out of a cube.  The scanned model is bumpy, so it isn't as perfect of a fit as I hoped for, but it is doing the job.