Alarm fob cover

Form-fitting cover for a DSC WS4939 Alarm fob, so that it doesn't activate my ear-splitting house alarm from my pocket. It may just have saved my hearing.
The cover slips on and off the fob easily but seldom pops off by accident. There is a port for reaching the disarm button without popping the case off.
Includes an OpenScad file, so in principle you can customize it to your own keychain fob.