Thanks, @gasspence & @MarkHunte. Both these approaches worked for me.
It would still be nice if a wider range of CSS cursors were available within Hype. Even if it is only the standard ones.
One thing I did notice was that these external CSS styles only work on elements where the cursor selection had never been altered. Once I changed this selection, Hype seen to add some behind the scenes styling that overrode anything I did subsequently, even if I just changed the setting straight back to "automatic".
By way of example, here is @MarkHunte's example file that worked fine until I briefly changed the cursor selection. Even though it is changed back now, the external CSS styling no longer works.
customCursorRuined.hype.zip (21.8 KB)