I just grabbed a pair of the Burco mirrors off of amazon, and they are way better than I expected them to be. I've gone through two sizes of the little adhesive spherical mirrors on both sides, and I'm glad found the burcos on this thread to replace them. I felt like even with both sizes of the spherical ones I was still having trouble seeing right behind the driver/passenger window even when those add-ons were almost 1/3 the size of the mirror. These replacements really fill that void by opening up the whole mirror and being able to see into the massive blind spots.
The install was pretty easy with the adhesive pads they provide in the box, but they didn't provide a whole lot of contact as my mirrors are flat and the burco replacements are curved. Also the four adhesive pads provided for each side are really thin, and seem to only contact the new mirror right on the edges if at all. My driver's side stuck well to the original mirror using the pads, but the passenger side didn't (must not have lined it up well enough) so I grabbed some silicone glue and put a hefty glob on and that did the trick.
I would highly recommend grabbing some of them if you're still looking for a solution:
Buy Burco 5731W Right Side Replacement Mirror Glass for 16-17 Mercedes-Benz Metris: Exterior Mirror Replacement Glass - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
www.amazon.com