I own a Zumo 660, and to my surprise they don't offer a decent sun shade for this sat nav. Tom Tom does. So, I asked a friend, who owns a 3D printing company to design a similar option for my 660. I picked it up this morning, and am very pleased with it. It looks great, and fits 100%
The price is €25 (around £20)
So, if some of you are interested to have a similar extra for your Zumo 660, just let me know.