BIG ELDER DRAGON JEWEL

How can i get big ed drgn jewel..?? i have slain so many elder drgn like kushala daora teostra and chameleos(all G-rank) and i dont get any...
i also have used mega lucky cat skill and luck booster...simply tell me how to get one...

try going on a kushala daora slaying quest and then equip the final chameleos armor and weapon wyvern blade "Holly" G. if you're relentless in pounding in enough damage, you can kill daora (G rank) in one encounter (yes, it's under the 25 mins. time limit before it tries to escape). he's the easiest one to drop elder dragon jewels.