Two ideas for you. Purchase a cheap Atlas Editions Normandie and cut the bridge wings off that and file and fit to suit your mercator model. The Atlas bridge wings are more rounded than Mercator's and are injection moulded plastic.
Swallow your pride and ask me to use my mould to cast the bridge and fore funnel from the Coastlines mould in polyureathane resin. Of course, the bridge wings will be identical to a Mercator model because I have the Mercator pattern and that was used to make the Coastlines mould.