SSIA~
DR680-any favorites or preferred battery's they have changed some sine I bought the ones I have.
The thing about your question is that I don't think there are ANY 9V DVD batteries widely available anymore, so answering your question is kinda hard. Now and then, you'll see a batch of the IMPACT RB270's show up on ebay or in other isolated places. I'm not sure how much I'd trust those though because I don't think they've been manufactured for awhile now so shelf life would be a concern even if they're in new, unopened packages.
Best bet in my estimation is to look through this forum at the feedback people have been providing on the new generation of universal batteries that are showing up and pick one that seems reliable, meets your budget and has a manual voltage setting scheme with a 9V setting.
PS: The exception of course would be the Tekkeon. People have stated that this battery doesn't play well with the 680 because it has an automatic voltage sensing circuit or some such logic.