There are mixed opinions about frame sliders, some say it concentrates the force of the crash onto the one point and damages the frame, if you slide on tarmac and then hit soft stuff it digs in and then can cause the bike to flip.....causing more damage.

There are no known frame sliders being made for the NSR that I am aware off, you can always make your own up. I have seen bikes with significant cosmetic damage even with frame and axle sliders.

In the end, I would accept reality, it's a track bike, be prepared/willing to fork out if you do crash it,