There's no public ROM and the game was lost forever. Once you turn off the game, it gets deleted.
For those who don't know what the original game is, it's a mini-game you could download on your DS at the Pokémon Park in 2005. It's a (non 1:1) remake of the lost DS Download Play game PokéPark Fishing Rally DS where you need to help Professor Grand Oak to study the Water fauna in the Brave River of the Antarsia Region.
