This fits this cashbox: https://a.co/d/2F6zHYv
The box is available in several different colors and has a combination, which I like so I don't have to keep track of the key between events. The only issue is that I usually travel with this in my carryon luggage particularly when it's full, but then if it gets turned on its side or upside down (this always happens) anything in the coin trays falls out and I either have to empty them before I start or else sort through everything once I arrive.
Sadly, this item is 11.5" wide so you need a large printer – it was designed to be printed on a Prusa XL at .32 layer height. You can see in the photos that I put a logo on mine, but the included file is just flat and you can do with it as you please.
Not sure how many people can use it, but hopefully it's helpful to someone! I've included the f3d file in case that's helpful as well; it's parameterized so you may be able to adjust it for other cashboxes.
The author marked this model as their own original creation.