Boobpedia, but again, the info might be not trustworthy/outdated* (
example)
There is also
Babepedia, which I view as similarly not-so-trustworthy (
example)
And a third one I know is the
Freeones bio tab — same, I wouldn't use it for anything "official" (
example**)
There was also at least one source which has the functionality for the stars to confirm their bio, but I don't remember now (maybe it was Freeones actually, at some point, but now I couldn't find any "Verified" labels there)
In any case, possibly the closest you can get to real data (without becoming a spy/stalker... or boyfriend and measuring yourself) is looking for
their official sources like Twitter (as I understand, it is more common for Japanese women to share their "three sizes", blood type etc. if they're models, actresses etc.)
But even then, even if the info is firsthand, it can become
outdated if it's from a long time ago
* Though they have links to external resources as proof, that source might not be trustworthy as well
** Wait what, has Hitomi retired?