For really unusual vegetables you can actually buy, simply search out a suitable Asian grocery. You should easily find gai lan, sin qua, kang kong, the choy family, daikon (and other radishes), cucurbits such as bitter and fuzzy melon, kumara (and yam and other sweet potatoes), lotus root, cloud ear (and cepes and other fungi), cooking bananas, taro, plus a wide range of beans, peas and lentils.

If you find a friendly place, they can be very helpful with recipes too. I got a great recipe for borlotti beans from a Lebanese green grocer.