We don't have a "native" Opera extension, however, it is possible to install TubeBuddy on Opera with this simple trick:
Install this Opera Extension which allows you to install Chrome Extensions directly in Opera - https://addons.opera.com/en/extensions/details/download-chrome-extension-9/
Install TubeBuddy in Opera from the Chrome Store: https://chrome.google.com/webstore/detail/tubebuddy/mhkhmbddkmdggbhaaaodilponhnccicb
Done! That's it.
Bonus: you can now install ANY Chrome Extension on Opera in the future :)