If you're only looking to store a small amount of data then writable discs (CD, DVD, etc) are still easily available. Just make sure to keep them out of direct

If you're only looking to store a small amount of data then writable discs (CD, DVD, etc) are still easily available. Just make sure to keep them out of direct sunlight as that can affect their long-term readability. If you need to store a larger volume of data then you'll probably be looking at tape of some form of hard disk/SSD. Either way you can reduce the risk of loss by having a regular process of copying the old data to new media and keeping both the old and new media - that way if one copy of your data fails you'll still have other copies that you can use.