Loved the original model, but immediately found a flaw -  batteries will become loose if you tilt it not that far. This is just a quick printing insert to keep the batteries retained when the top is closed.
 

Process:

• Loaded the meshes into Fusion

• Converted the meshes (not parametric as I do not have the paid version)

• Moved the converted meshes into alignment

• Filled all the slots with an outline of a CR2032 battery but slightly wider

• made a cube and trimmed it using the walls of the box top, and a manual bevel for the corners

• rotated that cube using the center of the hinge as the pivot point 180d to cover the battery models

• cut out the batteries from the cube

• created a plane that started at the edge of the box, rotated to meet the top+hinge corner of the battery cutouts

• planar split to the cube

• added a 1mm chamfer to the bottom to aid in insertion and printing
   

Printing:

• PLA (same as used for the box for me)

• 15% infill

• 2 walls

• Cubic infill pattern

• .20 nozzle

Installation:

• Press into top of box, with the lowest part facing the hinge

• I didn't need any glue, but obviously if its loose, glue the top so it stays in