You can find filing cabinets, remove the paper holding bits of cardboard in them and then you've got 3/4 large drawers to put stuff in. Filing cabinets in many places are lockable as they contain data such as personal records or company data so the manufacturers know the industries value them plus they're usually fully metal and the keys are reasonably safe. As long as you're just looking to keep a few nosey people in your house out it will do fine.