Well, not sure where you are or if this helps at all, friend, but a quick google search where I currently am (Australia) brings up two schools in Sydney both teaching what looks to be traditional Tenjin Shinyo Ryu, albeit with aikido in one instance. Hope this helps;
Hmm Ueshiba only studied Tenjin Shin'yo Ryu for a couple of months so I'd be less sure of saying that it's "the style" he came from...
That said, yes, there are Tenjin Shin'yo Ryu dojo around the world Paul Masters holds a Menkyo Kaiden, and his son Lee a Menkyo Paul teaches in England, whereas Lee currently heads a school in Sweden then there's the dojo in Australia I've heard of other dojo, but don't know if they're currently running. Paul Masters often holds seminars acting as introductions to the Ryu and it's methods around Europe.
EDIT: Yes, you'll struggle to find "authentic schools that teach this Koryu", as that's not the way it works you don't find authentic schools that teach the system, you find dojo of the system itself. It's a subtle, but very important distinction. Besides that, Koryu in particular are, by their very nature, not something you're going to find in your backyard, unless you are very lucky, and even then you're not likely to find the exact Ryu-ha you're wanting. If you want it, be prepared to move, or travel a great deal. If you're not prepared to do that, well, the Koryu aren't for you.