A number of years ago I bought a box of ume tea, in single-serve
envelopes, at buddhist temple in Japan. It contains only powdered ume
(a kind of plum) and some kombu (kelp)--no green tea. It's completely
powdered; you just stir in hot water and it's ready.

I'm running out and have not been able to find any online or locally so
far. Anybody have a source?