Fire some time I have been trying too find a good way to store sanding disks.
After many failed attempts using various containers a shop made container seems to fit the bill.
Made with a glue up with 2 prices of 1/2 inch mdf drilled with a 3 inch forsner bit.
The lid is 1/16 inch fiber board. The lid is latched shut with two sets of rare earth magnets. Gold duct tape forms a hinge.
For more grit choices create multiple wallets.