KALLAX Containers
Since Costco hasn’t gotten back to us, we’re going to promote another department store to you: IKEA. As you already know, IKEA sells some pretty wonderful stuff, from mattresses to carpets and storage shelves. However, the focus of this post isn’t the shelf but rather, what the OP stored in it.
They just so happened to find plastic containers that fit beautifully inside of each KALLAX compartment. With a label maker, the OP has no excuse for mixing their stationery with cables. Also, as you can see in the top-right corner, they even have a cubicle reserved for empty containers! Genius!