Available for 3D printing, CNC an laser cutting, the "Key"per uses an o-ring to secure your keys while retaining an ability to quickly swap keys in and out.

The o-ring used in this design can be found at most hardware stores, the colorful versions I've used can be purchased on etsy. If you can't find the same o-rings (specs below), you can change the design of the notches to fit whatever size o-ring that is available.

O-ring specs: 15mm OD, 10mm ID, 2.5mm thick

SVG file for CNC/Laser Cutting also provided