I've seen US-grown wasabi at some specialty stores in San Francisco.

It looks like there's actually a farm in Half Moon Bay producing it: http://www.foodgal.com/2014/04/californias-only-grower-of-re...

First year, so I'll let you know. We've grown horseradish for years, and that grows like a weed - it's almost invasive.

There is a UK company which grows Wasabi - https://shkspr.mobi/blog/2012/10/fresh-wasabi-in-the-uk/ - absolutely delicious. Bit of a pain to ship and keep fresh, but well worth it.

I've also found a place which imports it from Japan and the USA - https://shkspr.mobi/blog/2012/12/more-fresh-wasabi-in-the-uk... - which may be closer to where you are in the world.

My reading of that link is it's difficult to grow commercially, which is a long way away from difficult to grow in your own garden.

Could be. Here's one thing in Oregon, not sure if it's what I remember, but I don't think so because it appears to be a going concern: http://www.oregonlive.com/foodday/index.ssf/2011/10/real_was...

"Mountain streambeds are the plant's natural habitat. Though some Japanese wasabi is cultivated in soil, the highest quality product is water-grown, with plants sprouting from gravel-laced terraces through which streams are diverted."

Still sounds tricky compared to a lot of stuff.

Makes it sound perfect for aquaponics.