I bought a faux-aluminum case from Harbor Freight to neatly store my soldering station and other related tools. The case comes with movable dividers in various sizes, but not the sizes I would need to keep the larger components from sliding around.
This divider is modeled using OpenSCAD, so you can just punch in the number of segments you need, and a divider of the corresponding length will be generated. I didn't really need a fancy divider like this with slots for more dividers. A simple flat piece would have worked, but I figured if I was going to do it at all, I may as well do it right!
I uploaded several STL files at random sizes as well. Just in case!
The dividers match these cases from Harbor Freight, but I wouldn't be surprised if it they fit well in other similar cases.