ebay is your friend.
try searching for it on amazon too.
i had a similar problem when i wanted sonic the hedgehog for my gameboy advance. it was really impossible to find and when i did find it (in chinatown in NYC) it was REALLY expensive.
i tried to haggle with the guy behind the counter (since these videogame stores are own independantly in chinatown) but he wouldnt budge. thought i was taking advantage of the "law enforcement discount" and declined.