Chef Jimmy, look for purple yams. It's an off-shoot of the Okinawan and Peruvian purple sweet potatoes. It's common in Filipino cuisine where it is called "Ube". Check with your purveyors or you might want to try browsing or calling up any Asian markets in your area. If you know of any Filipino stores that sell produce that would be another place to try. If you know of any Filipino restaurant you could also try asking them.
BT, wakame is similar to alaria, another type of sea vegetable. It's the seaweed that you find in miso soup. It doesn't really have that strong of a flavor in the dish, but you can detect the taste on your tongue. It's not a flavor that stands out, rather a flavor that blends in with the fish.