Had the same question a while back, found an outlet here in California that sells the Shuguang at $55 each, sells matched pairs too. Greenstone USA is the name of the company (I have no affiliation).
I ended up buying the Electro Harmonix 300B from a different company for my Canary Reference 2 and paid just a little bit more than for the Chinese ones for the 2 Octets I needed.
Best of luck
Peter