The Yorkshireman
Well-Known Member
I was looking at those last week to run 2 400's side by side in cooltubes.
These are the cheapest.

http://www.ebay.co.uk/itm/Ducting-Y-Splitter-Piece-Extractor-Fan-Duct-Pipe-For-Ventilation-VENT-125mm-5-/160696437969?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item256a410cd1
My 5" 'Vents TT' fan uses 28w on low and 38w on high.