I beat the elite 4 1 month ago.Bit i still couldnt find latias.
if u have a gameshark u can use the battle latias/latios.
Battle Latias/Latios [R+Sel] AE45D69EADF606BC3C33D902BBBC78434C16
and u can change from latios to latias if u want with the gameshark
Choose Latias/Latios [L+Sel] AE45D79E2DF606BCBD3359023B3D7845CC00
or use the complete pokedex code now u can see the location of the lati u chose on ur pokedex. There a complete pokedex code for both AR and Gameshark.