There is no ppa for opera, for a couple of reasons. First, opera has its own repo, which is this, and it has been around since I remember using opera
deb http://deb.opera.com/opera/ stable non-free
Second, opera is closed source and launchpad (home of all those ppas) only hosts open source projects.
Finally, when you install opera from its deb file, apt also installs its repo and the key for it, so there is no need for the user to do anything more in order to update opera.