Just my 2cents on how I would find it.
1) Go to where cars get repaired.
Like a body shop....a cheap Honda repair shop....or even a Toyota.
Take a pack of smokes with you....lol.
Strike up a conversation.
Start talking to someone and ask him, where can I get a:
CAPA certified fender for a 2008 civic 4dr.
In Canada there is APT auto parts.
Pro body parts.
Then look up that company and ask for fender for your car.
M series, not sure where.
But reg BMW parts are available.
Now don't mention BMW to your new smoke buddy....lol
He wont know where to go for it.
Ps: I rebuilt BMWs only.
I strongly recommend getting from wrecker, as you will get OEM.
Most certified fitment parts are ok, but, there is no substitute, for OEM.
There is always something off.
Hardly noticeable, but if I point it out, then it will eat you forever.