In case anyone is desperate:
Japanese company Last Resort, who arrange working holidays and homestays for young Japanese, have started a new campaign which involves giving away free Tim Tams at all their branches until January next year. Their main office is in Shinjuku but if you need a quick Tim Tam fix then you can find branches in Ginza, Osaka, Sapporo, Kobe, Chiba, Yokohama, Nagoya, Kyoto, Hiroshima, Fukuoka, Omiya and Sendai