I like to have a small flashlight in my luggage: a bright one that runs on two CR123A Lithium batteries: they have a long shelf-life, and don't leak, make the flashlight powerful.

Unfortunately, these flashlights typically have a push-button switch to activate them, and if they get turned on in your luggage (easy enough when packing) they run the batteries down to nothing, and some flashlights get hot enough to cause concern about melting thin nylon in luggage, backpacks, etc.

I made this clip-on button protector to stop accidental light activation, while leaving the light ready to use pretty quickly. It just clips on the button end. Take it off when you need to use the light.

The size should fit most 2-battery flashlights. The example is fit at 25.3mm diameter, with an 18mm recess for the button. If you need to, you can scale it to your needs in most slicers.