Protector for traceable keyring

So, this might not be interesting for most people, but anyway.

I have a special keyring for my motorcycle key (and other keys as well). It is a small metal brick with a number on it, that is registered at the local police. If I loose my keys and someone finds them, they can be traced and returned to me.

The metal brick is 16mm x 52mm with rounded ends (r=8mm) and is 2mm thick.

Problem is that the steering stem on a motorcycle is easy to damage with a metal keychain. :(

So I came up w