I suspect you can find it at Asian (specifically Japanese) food stores, as well as some specialty coffee shops ... I think I've seen it at Coffee Bean; I know Blenz sells a matcha kit, though it's expensive, and I think they're only in Canada anyway. Starbucks sells matcha drinks but I don't know if they sell the powder ... I've found the best prices and selection at Asian food stores. The price varies widely and is probably a good indicator of quality, but for a mutt drink like this, the cheap stuff is fine.

More blueberries for me! Ahahaha!