If you have a Yubico Yubikey Neo, Standard, or U2F key as pictured https://www.yubico.com/products/yubikey-hardware/ -- this is a cover that will allow you to keep the Yubikey on your key chain while also protecting it from scratches, dings, and stress. It slips over the Yubikey and allows the key to be pulled or pushed out only with direct force from one of two directions.
I have included the STL and SKP files for your own modification.
The following settings were used in printing on a Makerbot Replicator 5 using standard black PLA.
.05mm Layer Height
40mm/s while extruding
80mm/s while traveling