|Tomppa Venture-Lieutenant, Finland—Turku|
Unfortunately, no. Karambit is from the fists of the ruby phoenix adventure path volume and thus, it isn't accessible through the normal means.
Playing through the AP would get you three chronicle sheets (one per book), it is likely (but not guaranteed) that the Karambit would be on one of those chronicle sheets. Getting a chronicle sheet with the item would sidestep the need for World Traveler boon, though, since you automatically have access to items on your chronicle sheet.
Additionally, I think World Traveler boon text may be outdated - it might not list Tian Xia as one of the regions you choose (but this is irrelevant for this particular case anyway).
That being said, the Treasure Vault book will become available in a month, and it'll have weapons in it. It's been speculated that some weapons from adventure paths may get reprinted in it, so there's a chance you may find Karambit there.
Lastly, unless you're a fighter or a human (unconventional weaponry feat), Karambit (or any Advanced weapon) is a poor choice for a weapon, since if you're relying on the weapon proficiency feat it will never grow your proficiency above trained. This means that you will be at a -2 to hit from level 5+ onwards (compared to martial weapons) and it'll only get worse the further you go.