The 22-year-old winger returns to the UK after spells with the PNG Hunters and Mount Hagen Eagles.
He will link up once again with compatriot Mark Mexico, with whom he played during a brief and ill-fated spell at Newcastle Thunder.
“Garry is someone we have known about for some time,” Eagles director of rugby Mark Aston told his club’s official website.
“He is explosive, he is powerful and he can score tries. He is a winger who is still very young, and like a lot of our signings he still has great potential to improve.
“It didn’t work out at Newcastle for whatever reason but he has real talent and we are excited about working with him.
“We have three great wingers at the club now with Ryan Millar and Rob Worrincy so we have the competition for places that we are looking for.
“Our backline has now been significantly strengthened, we have some real quality here and they all bring something different to the side.”