So, some searching around Michaels.com (thanks @lyndon!) lead me to the idea of plastic/acrylic collectors display boxes. They didn't have the size I need, but I looked on amazon for bigger boxes, and found that they make boxes for model cars that are about the right size. At that point, I hit myself over the head, as my boss literally has about 100 model cars, in these boxes, festooned around his office. In short, the answer has been staring me in the face since before I even started this project.
Boss is going to bring me some of his spares tomorrow, I'll post back with more info & hopefully pictures!