Hi @wap3com, you can *download the DEB and try to force apt-get to install it with "--force-yes" switch - you should be fine.
Seems like Opera's peeps packaging it for Debian based distros should have a look at that one.
*In case you don't know: apt-get download Oper's-package-name.deb.
Alternatively you can use dpkg -i --force-all downloaded-name.deb, or use any UI based package manager like e.g. aptitude to force install it.