Metal gasket, to cylinder head: 17173-70050 (2 needed)
Gasket Rings 2x, to Y-pipe: 90917-06046 (1 set)
2 Nut bracket: 18495-46020 (1 needed, or use your own 10x1,25 nuts)
But- if all comes off without hassle, you may be able to reuse them, especially the metal gaskets. Officially the manual says you should not reuse them.