please help! where to get lvl. 3 key spheres?

[me19875]

somehow, i have only received one lvl. 3 key sphere throughout the game, i have several lvl. 4 ones, but no lvl 3 ones. i just got the airship and 2 of my characters are 10 levels backed up because i cannot get past the lvl. 3 locks! where do i get some?

 

[Donald Trump]

go to zanarkand and fight those big robot monster guys, they look a lot like defender X and you get 1 lvl 3 key sphere for each, 2 if you overkill it

 

[Soul Saver]

I need not just level 3, but level 4. What about those?

EDIT:

I found one lvl.4 key sphere in a chest in a small enclave near where you fight Seymour on Mt.Gagazet.

I don't know if it was a good idea to use it to unlock zombie attack, though.

 

[Toothache]

Level 4 Spheres you can get by Bribing Chimera Brain in the Calm Lands. The general rule for bribe to be successful is to offer 20x their HP, and Chimera Brain has 9,500 HP iirc, so try about 190,000 gil.