I used a Slip-Grip RAM mount on my SV650 for my iPhone 5--worked great (sold the bike). You have to pick if you want it for a specific case, or no case. IIRC, my buddy dropped the bike which broke off the tab that holds the phone in--but he did drop it on that side.
Since I'm too new to post links, just Google Slip Grip Car mounts. SLIP-GRIP-RAM-HOL-HOLDER for Samsung Galaxy Note 8 is the one I would probably get (unless you ride in inclement weather; then consider one that allows a water resistant case).
This one also needs the appropriate RAM mount for your bike--RAM makes a center mount and a handlebar mount (might even be others). The nice thing about buying this separate is that you can always keep the mount, but upgrade/change the phone holding component later.