i looked into it and got an answer u might be looking for.
pepsi ice cucumber has actually been released on june 12, 2007 with limited amount.
official statement by the reseller suntory (in japanese)
http://www.suntory.co.jp/news/2007/9803.htmlarticle in english by japanprobe
http://www.japanprobe.com/?p=1980but according to some major japanese forums it got mostly bad reputations about the flavour

and they said it already disappeared from market in aug~sep 2007.
so when u came to japan it was too late to buy it.