I've not had problems with the Takegawa gasket but you can buy copper gaskets from Yuminashi if you need them.
Pretty cheap actually. 63.5MM (0.5MM) COPPER GASKET SET (MSX/SF ● GROM/SF ● MONKEY 125)
Pretty cheap actually. 63.5MM (0.5MM) COPPER GASKET SET (MSX/SF ● GROM/SF ● MONKEY 125)