Hi daftshadow,
we don't support opera officially.
But as it is based on chromium then chrome extension actually should work there (I believe we are talking about the one based on blink).
If you are interested in guide how to make it work in there ping me PM.
Note that Avast Safe zone browser is based on opera as well and it already has passwords extension bundled so you may consider it as replacement of original Opera browser.
Regards,
Martin