I have been unable to get black replacements for the two Shift keys, space, and Enter. (And two keys, backspace and numpad Enter, are missing stabilizers so they feel a bit limp.)Unicomp sells replacement insert stabilizers. And you might be able to get black blanks from them for the mismatched caps.
Back in the day I did use one to make the ideal all-black, all-IBM desktop:That was a gorgeous setup!Show Image(https://farm8.static.flickr.com/7145/6851350945_2128400407.jpg)