A version of the Magsafe Clip that allows you to tether the clip with a string or rubber band rather than clipping it to the cord.
The adapter is designed for a VERY snug fit. In fact, when you insert the adapter into the clip, you will remove a small amount of material from the inside corners of the clip. It will take some work and patience to get the adapter into the clip. But once it's in, it will be very snug, and should hold for a lifetime of usage.