Your research is very impressive. I did not think about looking at Japanese stores. Though I found some shipping information about a load of ukes from China.This is a google translation from Japanese Language website of UkuleleHouse in Waikiki :
MY NAME IS HANOHANO UKULELE. Actually, it's a brand made independently by LEOLANI craftsmen.
I lasered the design ukulele, which was just a toy, into a very good ukulele.
It's a ukulele limited to Hawaii.