As a general comment on these hinges (I have a 2009 331) I have experienced these hinges suddenly become very stiff and seize solid due to lack of lubrication. If you then use significant effort to open the door the pins can snap. This may be what happened to your missing hinges. The solution is a good squirt of WD40 on the hinges before moving them, wait 10 mins and they will be free again. You can then generally lift off the door and clean the pins. Luckily, I have avoided snapping any so I not needed to look for a supplier (yet).
kind regards, Andrew Bell.