Final Attack Materia?

I’ve been trying contantly to get this materia for two days now. In my FF7 strategy guide, it tells me that the Final Attack Materia is obtainable as a "chocobo racing prize". Well, I must have gone through a hundred S-Class races with my Gold chocobo, and the "Final Attack" materia hasn’t shown up once in the prize box thing. After a few races, Ester stopped me and said something like, "Wow! I haven’t seen anybody win so many s-class races since Joe." and then she gave me a bunch of items, but the final attack materia was not one of them. Any help?

One will do.