Locking drawers of various size. A couple of these and you wouldn't need a vet box!
Stackable Chicken Coop Cubbies: For toy storage, craft supplies storage, etc.
Garage organization. More
Image result for festool stackable tool boxes
DEWALT TSTAK II 13 in. 1-Compartment Flat Top Stackable Tool Box-DWST17807 - The Home Depot
Ridgid has come out with a new line of stackable tool boxes, and also a new cylindrical tube-shaped tool box as well.
Stackable tool boxes.
I want this for my EDC gear & such
Stackable Tool Boxes, Price Varies
Trusco Small Trunk Tool Box - $35