Ezy Storage Black Water Proof IP67 Storage Solution - YouTube
Ezy Storage Weather Proof IP65 13 Gallon Plastic Storage Bin Box w/ Lid (5 Pack) - Walmart.com
Probably the most space efficient airtight (waterproof) box for 12 spools and some desiccant - "Ezy Storage 32L/33.8qt Waterproof tote". Only about 1/8" space on top remains once lid is closed :
Ezy Storage Weather Proof IP65 13 Gallon Plastic Storage Bin Box w/ Lid (5 Pack) - Walmart.com
Ezy Storage 18-Liter/19-Quart Waterproof Clear Gasket Tote at Menards®
Ezy Storage Water-Proof IP67 - YouTube
Ezy Storage 75L/79.3Qt Waterproof Clear Latch Tote IP-67 FBA34064 - The Home Depot