Don't know why but it's always the left grip that fails(something to do with the clutch usage me thinks).You'll need to phone a breakers like Motorwroks and ask for a secondhand replacement.You can also buy new but they will be expensive(around the £100 mark!)
HTH
Bailey.
Honda VFR750 FV 1997 Red and dirty, 130K miles.
Honda VFR800 Xf Crossrunner 2016 White and dirty, 120K miles.
They'll probably tell you that the grips aren't covered under the warranty. Depends how helpful your local dealer is. See Minivin's comment.
Left grip is supposedly the one that goes most often as many folks grab that and manouver bike around while standing on the side stand side of the bike.