@DarkShadow.
Just finishing off installing my Viofo A119Pro, this afternoon. I've pretty much placed mine in the same spot you have yours mounted, just on the other side of the mirror. My Polo already has a dotted-hatch pattern printed on the screen behind the mirror so it hides it a little. I've had to mount it a tad lower than I would have liked, just to be sure the camera looks though a portion of the windscreen that fully swept by the wipers.
You could always buy a roll of black 3M VHB tape and simply replace the grey. I would imagine if you have a local sign writer they may well be able to cut you a vinyl template of some description. I suppose it may be possible to have a vinyl 'tint' cut. It's just a matter of drawing up a mask outline that looks like it came out of the factory and not something that looks like it was knocked up on 'Blue Peter.'
That said I suspect with where it's mounted within a day or so you won't even notice it. I struggled more hiding the wire completely so as to keep it all neat and OEM looking.