shiny legendarys

[ShinyHunterKai]

hi. im currently playing fire red on my GBA and i want a shiny mew two i know the odds of this are so high so i was wondering if there was a way through a rom hack and emulator i can cheat the shiny. i already have my save working on a rom on my mac after i ripped the save using a DS  but the shiny cheat code  i have is only for random encounter and i dont think it works or changes the odds in the case of legendarys. i know i can use PKhex to get shiny mewtwo however i'm picky and don't want it to be illegal.