yeah, go to gamefaq for more info. But if you really want it now......

have you found a way to Ancient Forest? I'm sure you do cause you already have Gold Chocobo. Now, Go to Cosmo Canyon with your chocobo and try to climb the mountain, the Ancient Forest look like jelly and covered by forest in world map.

Now, complete the challenge in the Ancient Forest and nab some handy stuff like weapon for Vincent and Red XIII, also Typoon and Slash-All Materia. Once you enter the cave search at the northern section, do not go out yet, just check in the cave, then go at middle and search the area and lastly check the southern section. I don't know if you can get it or not but GOOD LUCK.

the reason I ask you to check the cave fully cause I really don't know the place where you get Apocalypse, I have not play for a year so my brain probably have forget this. I did get it, I remember that I get it.