You can get it here. It's a root and runs about $100 a pound. I had a chef/client force me to try his sushi one day. The tuna was flown in overnight for Japan, real wasabi (he showed me the root) and white soy sauce. It was incredible. And the wasabi tasted nothing like that dyed horseradish stuff sushi places here serve. Much milder but more flavor. I don't know if I will ever touch that green clump on a plate of sushi again

Btw, the reason I said he forced me, I was extremely hung over because the night before we went out for sushi and sake after work. Then I went home and thought vodka was a good idea. The next day the idea of raw fish was the last thing I wanted. But it was amazing.