The generally accepted rule (not universally though, I don't believe) is the auto voltage selecting Tekkeon batteries wouldn't always recognize the proper voltage for the 680 and could fry the unit. You just need a battery that reliably puts out what it advertises. I believe the Tekkeons mistakenly supplying over 12v was what was causing issues for a few people.
I've had fine results with the knock off Naztech battery that was popular for a second (sorry can't find a link), as well as the old Tekkeon 3300 that saw a huge collection sold cheap on ebay a little while ago. I've also used 9v DVD batteries with no issue.
A battery that supplies a reliable 12 or 9v output should do fine.