cake frosting

Where can I get cake frosting in Japan? I looked at the import stores and even Costco and can't find it, is there some online shop (like for example on Rakuten or some other website)? Or at a physical store somewhere?

Note: Please don't suggest the Foreign Buyers Club FBC (as FBC takes months to send out orders and also FBC is a rip-off). Also please don't suggest making it homemade as I have tried this already and it did not turn out. (I am very bad at making sweets&baking items from scratch).

You can purchase ready-made icing in tubes or powder to which you are only to add water at Rakuten also CUOCA.
http://item.rakuten.co.jp/ultramix/c/0000000733/
http://search.cuoca.com/?ref=http%3A%2F%2Fwww.cuoca.com%2Fpro...
Cuoca has 4 physical shops - three in Tokyo and another in Takamatsu.
http://shop.cuoca.com/english/

If you are in Tokyo the shop National Azabu at Hiroo has readymade frosting. I think Meid-ya also stock it. There is one in Hiroo and one in Roppongi.

As well Nissan Supermarket and Deli at Azabu-Juban will most probably have it also.

Thank you both for your information, it is very helpful for me! :) again, thanks!