I have my books now.
Whip Dagger (Sword & Fist): Dmg 1d6 (Slashing), 19-20/x2
Nagaika (Masters of the Wild): Dmg 1d6 (Slashing), x3
Masters of the Wild actually mentions Exotic Weapon Proficiency (Nagaika), but I say if Whip and Whip Dagger are close enough to be the same, a Nagaika (essentially a glass studded whip) is the same too. The rules for Nagaika are otherwise identical to the whip dagger.
They are so similar that it would be silly to say nagaika needs its own proficiency, instead of sharing one with whip and whip dagger.