Unfortunately these are very hard to find. I got mine while I was in Japan. Have never found them here, albeit I probably wasn't looking in the right places to start.
i dont' know much about tea, but if you are in Toronto, i know there's a place called House of Tea (1015-1017 Yonge Street). Maybe you can call and ask
(416) 922-1226
otherwise, look in yellowpages for tea related stores