The cast iron rings are available from MG Cycle separately, but they are about 170 USD ea. Some Euro sellers have a stainless version for about the same , so unless Harpers or another Guzzi dealer has some NOS ones at a better price, thats about it. OTOH, if the thickness is still decent ( limit is 5.7 mm) and they are straight, Tom at Truedisk can do a nice job of grinding them and that would cost a lot less.