I have a KC84 but unfortunately in black and not white
Have you checked taobao?
For a white Keycool84, this price doesn't look bad (I think the black ones don't use the windowed keys)
Unfortunately
a) I don't need a whole keyboard (just a few windowed caps)
b) It isn't really possible to checkout using the Google Translate version of the website and I don't read what I presume is Chinese (though my wife has a friend that might).
They might have the keycaps I am looking for, but the term (windowed keycap) and variations I can think of don't return helpful results. Someone that can run searches using the correct Chinese terms might be able to help.