Fast forward 5 years later....
C. cordata zonatus has been folded into C. cordata grabowski which is endemic to Borneo.
Now, there's been a plant circulating in Japan as "Crypt. cf. cordata "West of Dayu" with code A-03 (I've also seen A-03C).
Might this be the same plant as that? Looks pretty similar, flowers in this species can be anything from white to yellow to yellow and purple.