None of my mirrors have suffered similar fractures so I can't really advise from
experience. But it seems from your photos that improvising a replacement
spring (or elastic) might be worth a try.

My recommendation is to mount the mirror to the door first. Then, while the
plastic cover is still off, do what you can to fabricate fasteners to secure the
hinged portions as solidly as possible. Once this has been done, then you
can slide the plastic cover back on - it should snap and lock against the
internal latch.

The reason why you should replace the spring with another spring or elastic
is because once everything is working and mounted back on the door, should
you ever have a need to remove the plastic cover again, such as replacing the
mirror itself, clean hornet nest, replace the rubber gasket between the mirror
and the door, you must pivot the mirror inwards in order for you to gain access
to the locking latch, thus freeing the plastic cover.

Hope this is making sense.

The spring is what sucks the mirror up tight. The outboard attachment point has broken, which is the cause of floppy mirrors. You need another spring and then you need to fabricate a new outboard attachment, which is what this thread is about. The hinge is a double jointed affair and may not be important, but since you need a spring, maybe a junk yard mirror might be in order.

wonder if you can try ghetto fixing it for now using surgical tubing. have someone put there finger in there while you tie the knot. ;-)

Raymond's link doesn't work some reason, but having bunch of W210 in family, I did the fix on at least 3 of them.
I was always able to stretch the spring with needle-nose pliers, twist it 90 degree and hook to the slot left behind broken hook.
Obviously when sprig is missing, you need find a replacement.

Was going to replace the mirror but definitely going to try this one first.

Thanks

C2 Turbo: do give the DIY fixes a try. Mirror replacement can be expensive so hopefully the home brew repair will suffice