Engine Who sells COPPER s/p inlet manifold gaskets?

All the usual suspects sell the silver alloy ones, but reading here suggests getting them to seal is problematic.

Anyone know where to get hold of OE spec copper inlet manifold to cylinder head sealing gaskets for 1500 s/p (same as 1300 AFAIK)

Thanks

PS: thoughts on using RTV to seal if I can only use the silver ones....?