I think I've found a solution for the database, at least for now. I've put all the hair-numbers I've found into the parts list under
"Wearable (Hair)", added pictures cribbed from various sources (thanks, picture posters!) and named them according to how I describe them in
"Who's That Klicky?".
They are not assigned to sets and will not be. Instead, on the parts page for each is a link to "Who's That Klicky" to show Klickies with that hairstyle and hair-colour; from there you can click through to find the sets.
Caveat: not all klickies may show for any certain hairpiece, since I tend not to assign a hairstyle if I don't own the klicky or can't see it clearly on the instructions. Corrections and additions welcome, ideally with photo-evidence!
Next step: linking backward, from results of a WTK search to the hair part, to get its number. More pictures to come, too.