It is a common vegetable plant in hawaii. When i lived there, i had it growing all around my community garden - and it can be very invasive. If you have a friend there, ask them for a little cutting, one with about 3 or 4 nodes. Also if you have any Vietnamese neghbors, you are bound to get get it from them.
I like the flavor when i put it in fish, but can be used on chicken and pork soup, too. It is almost like the leaves of pepper leaves so be sure you know what you are getting.