Door Locks

Hi Folks
Whilst refurbishing both my doors I find both doors have broken key barrels and no associated lever or operating rod going to the latch mechanism itself. Clearly the barrels should have a some sort of forked end which as it rotates works the lever but in both instances this little feature of the diecasting has broken off and since disappeared. Looking through the various spares catalogues, 2 facts seem to emerge:- Firstly the barrel at this location and the lever seem to have a weakness here and are prone to breakage, and secondly, the Retractable and Station Wagon are regarded as 'exceptions' and for some reason excluded from the other '57 offerings.
Has anyone come accross this problem and more importantly does anyone know where I can acquire new barrels, levers, actuating rods and keys, specifically for a '57 Retractable.
Many Thanks
JK