Why would you want to store it in a shed?
If it's important backup, and you wan to be sure it doesn't get destroyed in a house fire, a safety deposit box at a bank would make more sense.
If it's being "hidden" so another family member doesn't find it, buy an old hard cover book that's about twice as thick and cut out the pages in the middle so it can be set inside, and then close the book, so it looks just like a book when viewed on a shelf, and unless someone sees you cutting the pages out, no one will know, unless they pick up the book.
It's in case of theft or fire. I have thought about a safe deposit box, but the nearest bank is seventeen miles. I don't think I would end up keeping the drive up to date in that case.
Just a quick note that most Fire Proof safes will not protect electronics. They're designed to keep the temperature inside the box low enough that paper doesn't burn, but electronics likely wouldn't survive. I did a quick look and the high quality fireproof safes tend to only be rated to keep the temperature under 180C.Have you looked into the Fire Proof safes? They have all kinds of different models out, and I'm sure something could fall into your price range.