If you don't buy the materia it can be found outside later on, bottom right
just by the chocobo pen. The swamp can be crossed without a chocobo. either
A) wait until the zolom is in the near left corner of the swamp
B) save halfway or when you see the zolom approaching (need quick reactions
for the latter). reload and the zolom is placed randomly. you may need to
save and reload a couple times.

IIRC you need the highwind before you can start breeding chocobos.

it is also of note that you can strand yourself, but you have to go out of
your way to do so.

have any chocobo better than yellow. take it on the higwind. get off and
ride the chocobo back to the ranch. release the chocobo. you are
permanently stranded and cannot continue the game!

here's where you need to park the highwind
green - outside junon
blue - any continent other than eastern
black - either of above
gold - either of above