Really? "Purple Squirrel"?
Is that the best you can come up with to describe an 'unfindable' candidate?
I remember seeing red squirrels for the first time in 1976, in the Vienna Graveyard, while I made my pilgrimage to the tombs of Beethoven, Schoenberg, the Strausses, Schubert, and other great Viennese super-composers. "Rock-stars", if you will, to reinvent another overused phrase.
I had never seen red squirrels, before, so I was pretty amazed with them, as there were quite a few scurrying about. Nonetheless, I also later noticed many red squirrels at Princeton University, ambling about on the lawns, in 1977 through 1981. Usually, the Princetonian squirrels were greyish, as I recall, but the red ones had started to display themselves somewhat prominently by the time I was a Senior, and ready to graduate.
So, at this point, I want to reiterate that creating a 'Purple Squirrel' is easily within the grasp of Man's Technology, with genetic recombination, gene-splicing from phosphorescent jellyfish, etc. This particular term has come to an end of its productive life.
We must move beyond!
I suggest that we simply return to the vocabulary we already had, before the very odd "purple squirrel" phrase was even invented. Try checking out Jorge Luis Borges' "Book of Imaginary Beings" to be more original, at least more esoteric, and less banal.
Even T.H. White's "The Bestiary: A Book of Beasts" would yield more original linguistics turns and twists, which would hopefully allay the dreadful and oppressive boredom that results from hearing the trite and over-used phrase "purple squirrel".
Whatever happened to "Unicorn", "Bigfoot", "Chimera", "Elf", "Wood Nymph" or other much more plausible creatures than "P-U-R-P-L-E S-Q-U-I-R-R-E-L"?
If Recruiters are meant to be 'silver-tongued' advocates for companies, job offers, and opportunities, then we must rise to the occasion, and drop the use of unoriginal and all-too-common cliche's. So, next time you want to say "purple squirrel", please instead try "narwhal" or "oryx" (if the search is for a 'unicorn') or 'Tibetan bear' (if the search is for a Yeti), etc.
Let's get real, people! Use your words properly, to best effect.
No more "purple squirrels", please! They are much too easy to find, or at least invent.