I don't think that it will be really needed to use something as sturdy and expensive. A common iron block will be a lot more than enough I think !

last night i bought 5 usb sticks and 2 waterproof boxes,  i put the box inside of the other box then the 5 usb sticks in the middle of the box,  afterwards i went into my backyard and dug a hole underneath the bird fountain ... i plan to keep it there for 20 years.