Where can I get an exhaust Gasket?

[Enoch]

Thanks for the replies chaps, I think I will try the local exhaust centre first, I have some gasket material but I don't think it would take the heat from an exhaust manifold. I like the idea of making one from copper but will keep that as a plan b due to the time it would take to get it right.
Thanks again, happy building.
Enoch.
PS fitting my tank today and maybe the exhaust, will see how I get on.