Before I bought it I searched for some pictures and found nearly nothing, so maybe it helps somebody to decide. Bought from Germany, either Ebay:
http://www.ebay.de/itm/4x-Mooncaps-16-Z ... Sw1DtXF2~K
or directly contact seller at email@example.com
I love the design. As I have my leaf very shortly and drove only few kilometers without the caps, I cannot say anything about consumption, but think it is the same. It is winter here and I am all the time around 18 kWh. The only thing is that you can hear a little noise on driving, but nothing that would disturb much.
I also have to solve the security somehow, unfortunately somebody stole one overnight in the first week