you probably haven't been able to find it for good reason, its illegal to re-sale a copy of cakewalk pro audio (I want to say all cakewalk software is like that)
meaning the license is non-transferable.
you might have better luck moving up to Music creator instead.(kind of like a newer version of pro audio 9).
you wont have a difficult time switching from cakewalk pro audio 9 to music creator.
it's very close to and along the lines of pro audio, I know I used pro audio years ago.
great daw to learn on as well wasn't it ? :)