Gearbox drive sprocket, perhaps the hardest worked sprocket on the machine! Ensuring this is replaced at the first sign of wear may save the tricky problem of trying to find a new rear wheel sprocket.
It would be a good idea to renew this Sprocket Plate at the same time, preferably with the correct specification, new OE bolts.
Renew this before the damage is passed on to the rear sprocket. Why not order all the final drive components you require at the same time and save money on shipping costs with a multiple order.