ok the only way to get wings of discovery are as follows...
the easiest way for me finally is... defeat shinryu, you will get 2
you can bribe malboro for 540,000 gil and get about three every time... you can actually start out bribing him at 270,000 and just keep bribing him one gil after that till he flees... you will get about 2 that way...
you can also bribe great malboro... BUT thatll be 1,280,000 gil... for only 8....
and thats it my friend.... have fun and good luck with your patience... speaking from many hours of experiance, this will take you a while, well that is if your anything like me and i HAVE to have the best party possible... and your gonna get enough of those so you can put break hp limit on EVER armor for your characters... yea talk about being bored sometimes.....