Just FYI, if you need this (I’ve been looking for it for ages). There’s a stall in the JianGuo flower market that sells it, plus a whole bunch of other interesting stuff.
Starting from the Jade Market end, walk along the left-hand side until you’re directly underneath the beam (look up!) with ‘8’ painted on it. Walk another ten paces (the width of one or two booths) and look to your left. There’s a stall that sells nothing but herbs. They have an LCD monitor suspended in the entranceway declaring ‘$40/pot or 3 pots for $100’. Can’t remember exactly what it’s called now - some English name, a Japanese ‘的’, and ‘香草’.