The closest you'll find is
Otyugh, but that will only let you change current EXP/AP stats, not rate of growth. But at that point, you might as well use
Black Chocobo and edit your saves instead.
edit:
This trainer claims to have exp, AP, and money accelerators... but it only works with the 2012/Steam version. If you've got bootleg, it's a safe bet you converted your game to the 1998 version, which it doesn't support.