Really. Tracing paper seems kind of scarce these days.
Possibly because lightboxes are a lot fancier and not terribly expensive.
As opposed to the days when the author of a given "how-to" book on drawing suggests making your own lightbox.
Or going even further and suggesting you make your own drawing table, too.
I have a lightbox. Had it for years and barely use it. And I hear tell I could get a slimmer, more lightweight LED lightbox for maybe half the price I paid for the old one.
But still. Not a lot of tracing paper to be found...