Region Specific Subsets (Noto / CJK)

Noto offers region-specific subsets of Noto Sans and Noto Serif for the supported regions (HK, JP, KR, SC, TC). However, those subsets are not available for NotoSansMono (see https://www.google.com/get/noto/help/cjk/).

Can anyone suggest a way to distill those subsets? I have experimented with the FontTools pyftsubset tool and also the Adam Twardoch pyftfeatfreeze tool (https://github.com/twardoch/fonttools-utils) but neither seems to perform this fuction ...

... Any suggestions on how this might be accomplished?