Phil,
I talked to an exhaust specialist and he said my extractors are definitely custom built. They are 4 into 2 into 1 but are nothing really special (not tuned length or stove enamel, etc)and I am sure you could get some made up for not too much in Old Blighty.
Anyway, I will put the word out for some on your behalf as there are quite a few Longchamp owners and spares in Sydney (relatively speaking!) and you never know your luck.
Stuart
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