What alternatives do we have following the Vault discontinuation?

I like keeping my most sensitive documents inside this PIN protected folder, knowing that anyone who has access (or gains access) to my Mac will not have access to the files inside.

Now that Dropbox is removing this critical feature, what can users do to protect their most sensitive documents? The suggestions provided by Dropbox -- such as enabling 2-factor authentication -- are unhelpful because they do not secure the folder from someone who may have access to the machine, for example a child or a co-worker.