This pattern is part of the ebook, which is full of many Tildes and 3 Tilde vests. It is not available as a single pattern.

Two thoughts inspired me to design this Tilde: one, being
narrow, it progresses rapidly, and two, I am fond of keyhole
scarves and their propensity to stay put. But I had no idea how
beguiling the results would be, and so promptly after knitting
this one I knit another. You might too
I added a fin-flap to cover the opening because I could not
bear to leave it unadorned. It emerges like the upper field on a
Tiny Tilde (page 7 in the ebook) and finishes like a Tiny Tilde’s top fins.