Originally Posted by
fietsbob
a bit tidier , but harder to source, NL BBB, has a quill to go inside a short steerer,
and a bunch of keyed shim spacers, that make up for the quill being the tube ID.
Thing I've heard about those is that they're actually intended to be used as extenders for quill stems. ID for a threadless steerer tube may not be a good enough match for things to work, not to mention that a threadless steerer won't be expecting the expanding load generated by the wedge. Whether that's an issue or not IRL, I have no idea.