It is true that the 2010 repo does not have flash-player-plugin-opera but I have flash-player-plugin installed and run opera without problems on websites with flash. Can you give an example site that does not work in opera?
Alternatively you can get the flash-player-plugin-opera from the non-free section of the 2007 repo which installs with opera in 2010. However, the flash-player-plugin-opera requires to have opera, so you can not use opera-qt or opera-unite.
hope this helps,