Well, here's a site with the location up:
Shinagawa Station is about a couple of stops south of Tokyo Station (as opposed to Akihabara being a couple of stops north of it).
From there head East towards the water and you'll see where it was on the other side (as it will only be there until October 11th....).
....oh, and while you're in Akiba, can you see how much it would cost me to bring back a 1:1 Chii??