no need for spoilers for these one since they were on e16 or prior as well, but you get the audinite in a cave acessable in the north of apophyl, you'll need dive and surf to reach the cave(Its not underwater dont worry) and waterfall and blizzard to get the stone. once you get in the cave, climb up the first waterfall, get in to a battle, freeze the field with blizzard and a way to another part of the cave will be open, there you'll find the stone.
also if you buy an item in the flower shop in lapis ward(Dont remember the name, its the same you use for flabebe) and go to ametrine, a girl there says the she lost her necklace, give her the item and she will rewared you the bannetite