Ummm... it might be a bit of effort, but have you considered making your own boxes? I've done this on a number of occasions for various things that don't quite fit conventional storages items available. I'd recommend either two methods -
* build completely from scratch. Use heavy guage ply cardboard that can be bought from a hobby store or canabalised from packing boxes. Use a sharp hobby knife, heavy duty packing tape for holding corners together and strong glue for making joins. Since I've done balsa modelling in the past, I already had a lot of this stuff around the house.
* Alternatively, find a box that is generally sized to fit your needs, and use the heavy duty cardboard to fit compartments. This is a bit quicker and easier, but you have to be lucky to find something that fits the size you want... check out gift stores that sell greeting cards and wrapping paper (they usually have variously sized boxes for holding gifts).
In both instances, some strips of velcro can be used as the locking mechanism for the lid. A cheap can of thick spray paint from your local hardware store can be used to finish the job and cover up all the messy joins (if you use several coats, the paint itself can help give the box some extra strength).
As I said before, I've done this on a number of occasions for storing those unusual hobby items that don't quite seem to 'fit' conventional storage devices available.