When I was at the race track one of my friends already has an Ohlins installed on his 400. I know he raced the N300 last year so I would imagine he used it as a donor from his N300. I would have to agree with @Kiwi Rider the bike really doesn't need one. However if you feel you need one now look at the N300 as an option.Do you think mounting kit will be made for Ninja 400, to mount Ohlin or Matris steering damper?
I just ordered one from this company for my ZX6R. This is a cheap Chinese damper that got some good reviews. I figured I would give it a try. Some will say it's not needed for street but anything that helps me avoid bouncing off the pavement is needed IMO. For less than 100 bucks it's worth a try.