As far as I'm aware tempered glass screen protectors for the back only aren't available for the Galaxy Note 10. The closest thing you'd be looking at is a case that is constructed of tempered glass on the back.
If you want to go the no-case route, you'll have to settle with a vinyl skin from a manufacturer like Dbrand.
As seobro suggested, there is no tempered glass available for back side of the phone. However, you can get a case from the link down below from Samsung website.