https://bdocodex.com/th/item/55187/
https://bdocodex.com/th/item/55185/
https://bdocodex.com/th/item/55183/

Esse item é o de comercio ? ou precisa dropar deles ?

I used loot of normal desert naga and swamp naga (normal and commander).

The win condition for this quest is handing in three naga-themed items. Two you will be able to get easily; one drops from naga commanders and the other from regular naga.
The third one is where it gets frustrating. You have a choice of two items - one is a trade item obtainable from Ginta, the trade manager at Western Gateway - however to buy it you will need to have the Trading life skill at at least Apprentice 7 rank.
The other option is to travel all the way to the desert and kill some nagas there for the item that they drop - for which you will obviously need to waste time travelling there and actually have a gear level high enough to deal with the naga there.

Can confirm the following items work:

- Naga Webfoot (obtained from Swamp Naga near Glish)
- Naga Commander's Neck Ornament (obtained from Swamp Naga near Glish)
- Desert Naga's Webfoot (obtained from Desert Naga in Valencia)

- Desert Naga's Webfoot from Desert Nagas
- Naga Webfoot from Swamp Nagas
- Naga Commander's Neck Ornament from Swamp Nagas

I had to buy the Confiscated Naga Weapon (acquired from trading mentioned in a comment above) to complete this quest.

The Desert Naga Webfoot was not working for me.
Abandoned the quest, and reaccepted it, and was then able to turn it all in.

1. Жабра наги - падают с любой Болотная нага
2. Кулон командира Наг - падает с Болотная нага-командир
3. Оружие наг (трофейное) - продаются у торговца Гинта из Северо-западные ворота

エルビアに出現するナーガのドロップでは駄目です

Possible Bug: IF YOU HAVE THE 3 ITEMS AND KANNA DONT COMPLETE YOUR QUEST TALKING WITH HER, TRY TO RETAKE THE QUEST AND TALK WITH HER AGAIN.
Posible Bug: Si al hablar con Kanna la mision no se te completa, pero tienes los objetos, abandona la mision y vuelve a cogerla.