It is...it's available as an unlockable option for the Broadsword powerset with Weapons customisation, it requires the Tracer badge (defeat 200 Tsoo Sorcerers) to unlock it.
The reason it's in broadsword is because the Tsoo still use the Broadsword animations like Katana originally did.
Badge Earned: Wing Clipper
A real showstopper!
Yeah but surely it could be added to the Katana set? I mean, the Rikti blade isn't used by the Rikti like a katana but it's in their set. It just seems silly having it shoved into the broadsword set hen it doesn't really fit the theme. Plus it's the best looking katana in the game 
*cries*
The Katana powerset is two handed. The Hilt of the Tsoo katana is too short to be gripped with two hands.
NB the Rikti katana is different to the rikti broadsword.
I really should do something about this signature.
*cries more*
Maybe the Devs could create a 2 handed one? Maybe? Please? No?
:'(
Please oh please can this be added to the Scrapper set?