Reach Subway Town on the second disc. There is a man behind the shop that always "has a special deal". Keep checking back with him until he is selling Viper Rockets. Buy all you can until you have no money remaining. Go to the shop just steps away and sell them for a nine dollar profit every time you press A. Once you reach $9,999 (the maximum amount), purchase all the ingredients, schematics, and ammo desired.