You can still get FoV at least
from Gamersgate (currently on sale, even).
You may want to consider getting the Developer's Cut release, though, as it includes a remastered version of D2:ED and the add-on FoV. You wouldn't be able to continue with your D2:ED save, but could start another (level 35) character at the beginning of FoV and pretty much recreate your existing character.
If you do decide to go with FoV, once you are done with your current game, there is a
Flames of Vengeance to Dragon Knight Saga patch.
As long as you bought D2:ED (it was given away on a magazine cover CD awhile ago), you may be able to get a free upgrade to the Developer's Cut version of the game from the
Larian Vault. See the topic
Divinity 2: Developer's Cut and Anthology on Steam. This offer will eventually expire, but AFAIK is still valid; Larian support may be a little slower to respond than usual, as they may have a bit of email when they get back from Christmas break on Monday.
