My advice would be to defeat shinryu lots and lots. His ordinary item drop is 1xwings to discovery but you can get 2 for an overkill. You'll pick up Dark matters for his rare drop so you can get both of what you want from shinryu.

You CAN bribe Malboros for an obcene amount of gil... but we do not reason with these evil fiends... they must all be destroyed!

After you have however many wings to discory you want, find a quick and easily defeatable monster in the monster arena and kill it repeatedly. I killed one monster enough times to get maximum of their normal drop then moved to another. I reached maximum capacity for most of the drops in the arena while primarily aiming for Dark matters.

What do you want them for? Break HP limit and Ribbon? Dark aeons drop these weapons. Go kick yojimbos arse several times... he'll drop what you want eventually