In article , "Steve
Lowe" says...
The said ducting turned up this morning - but it's round !!! rang the
firm and they say they don't do rectangular which is not she told me
on Tuesday - so my question still stands - where can I get some 204 x
60mm flexible ducting.

Can you not make a custom piece yourself? Make up a cardboard
pattern then fabricate in soldered tinplate or similar.