The price depends on your dealer and his distributor.
Sprocket covers are:
1128 640 1706 used on MS 461, 461-VW, 461-VWZ, 461-Z, 461-Z Magnum
1128 640 1710 used on MS 461-RVWZ, 461-RZ (USA version)
1122 648 0403 used on MS 461-R, 461-RVWZ, 461-RZ, 461-RZ Rescue (big cover)