I really liked the parametric rugged storage box by Whity on Printables but I didn't like that once an insert is put into a storage box it's nearly impossible to remove it so you have to make sure the layout is exactly what you want.

I remixed the model, while still keeping it fully parametric, so that it uses a gridfinity base on the bottom which allows you to change the layout of what you have in the box and any time.

The lid has been shortened as much as it could be and filled in so that once the box is closed it's tight up against the top of the storage bins inside so nothing will fall out of each gridfinity bin you have inside.

I've uploaded 2x2 - 5x5 gridfinity storage boxes that fit 6U tall gridfinity bins in both 6x2 and 6x3 magnet sizes, if you're looking for a gridfinity box that's a different size you can download the parametric file and open it up in Fusion 360. You'll see under the custom parameters you have options for the number of gridfinity slots by width, depth, and gridfinity unit height as well as the ability to change the magnet size if you want to use different magnets.

There's also an included magnet test model for both 6x2 and 6x3 magnets with .1mm of tolerance (I found that was the best on my X1C to where I could still press fit the magnets but they were held tightly enough without glue that they wouldn't come back out on their own)