If you do not have a 3D printer and CAD software, you are 100% right.

If you already have those things like OP, then why not just design / print one? I am also a 3D printer / CAD person, and I love designing replacement parts that are wither too expensive, or often impossible to find. Mostly though, I design and print things that make my and my families lives easier / nicer / more convenient. And they are customized to the exact item and function, something that you would most likely never be able to get in a store or online.

Stove Knob guards. https://www.printables.com/model/278668-stove-knob-guard

Salt / Pepper Grinder Holder. https://www.printables.com/model/155219-salt-and-pepper-grinder-caddy

Spice Jar Organizer. https://www.printables.com/model/151171-spice-jar-spacer-organizer

Just to name a few things.

And now I need to make a 3D printed mold in a comfortable shape that can be used to easily cast concrete around a lighter.

Maybe a simple cylinder, with the lighter off center so it can easily be flicked?

Maybe I’ll squish some play-doh around one and scan it and use that.

Whatever, it just needs to be too big to “accidentally” end up in someone’s pocket.

• While “Safety Dance” plays faintly in the background.