I managed to get a Vulcan with TS3 from the BOff recruitment DOff assignment.
Fairly rare though, the Jem'Hadar mission reward is probably the easiest way.
"But in-game I have another name. You must learn to know me by that name. This was the very reason you were brought into the forums, that by knowing me here for a little, you might know me better there."
Apparently you can also get someone to train your Boff for you. Though, not sure how its done.
"The world ain't all sunshine and rainbows. It's a very mean and nasty place and I don't care how tough you are it will beat you to your knees and keep you there permanently if you let it. You, me, or nobody is gonna hit as hard as life. But it ain't about how hard ya hit. It's about how hard you can get hit and keep moving forward." - Rocky Balboa (2006)