It can be bought with the Serrice Council armory license (which is obtainable from Delanynder or Commander Rentola), or can also be rarely gained from drops at the appropriate level.
Addition: It can also be randomly ordered from the MSV Wallace once you've completed the quests in the "Pinnacle Station" DLC. Go to Admiral Ahern's retirement home and log into the computer, then pay 220,000 credits and get a random, high-quality item. Use the save/reload trick until you get what you want.
I've gotten Colossus X armor (human medium, quarian light), Savant X omnitools, Savant X bioamps, all sorts of Level X mods, Berserker X armor (krogan heavy), etc. I find that ordering randomly is much quicker for getting high level items than buying the licenses and visiting different vendors. The DLC costs $5, though, but I think the additional content is worth it.