How do you get synthesis items in Kingdom Hearts 2?

Answer 1

go to a moogle, one of those weird floaty things with the red ball on its head you'll find one in the first part of hollow bastion where there are no enemies, select talk (triangle) and go down the list of options till you see synthesize press X and you will then have synthesized all your gems, shards etc. make sure to check creations and free development reguarly to check any items you can get if its in white you can get it if not keep trying and look for the items on the right side of the page. these are what you need to make the shaded item.

Answer 2

They're either found in treasure chests,or when enemies drop them after being defeated.A good way to help your chances to get them is to equip the ability lucky lucky for Sora Donald and Goofy.You can also equip lucky ring,and all the lucky weapons.