I have a client who has a Wordpress blog and he'd like to give a small number of clients their own user accounts in which they'll be able to access a specific set of files. These files would only be visible/downloadable to users to whom the files are assigned by the site administrator, not all users.

In example, if Bob and Susan both had Wordpress accounts on this site, the site owner would be able to upload a file and assign it to Bob and that Susan would not be able to see. Bob and Susan wouldn't need to add files, just have access to files provided by the site admin.

I've Google'd around a bit for a plugin that will allow this, but I'm not finding anything. Does such a plugin exist?

Similar question of that: File Storage Plugin (For Individual Users)? but that it's over 10 years old.