1.First, obtain about 50 pounds (110 kg) of weapons grade Plutonium at your local supplier (see NOTE 1). A nuclear power plant is not recommended, as large quantities of missing Plutonium tends to make plant engineers unhappy. We suggest that you contact your local terrorist organization, or perhaps the Junior Achievement in your neighborhood.Chey. I didn't know it's that easy. Piece of cake mate.
2. Please remember that Plutonium, especially pure, refined Plutonium, is somewhat dangerous. Wash your hands with soap and warm water after handling the material, and don't allow your children or pets to play in it or eat it. Any left over Plutonium dust is excellent as an insect repellant. You may wish to keep the substance in a lead box if you can find one in your local junk yard, but an old coffee can will do nicely.
3. Fashion together a metal enclosure to house the device. Most common varieties of sheet metal can be bent to disguise this enclosure as, for example, a briefcase, a lunch pail, or a Buick. Do not use tinfoil.
Important: Please do not try to build one and explode it in your neighbourhood. This is only for educational purpose. I repeat. Only for educational purpose.