R1kku has the same idea I do, get a piece of PVC pipe, about 4" in diameter, they come in 8' sections. Cut the pipe to match your height and such. Then get either some insulation foam and cover it with glue and craft foam, use this to make the back end of the bazooka. The blade can be made similarly. The craft foam/insulation foam is light and easy to work with. You can then use that for the bottom section that holds the blade. You can get another piece of PVC pipe to fit the blade into and slide it into the hole of the bottom of the bazooka. The bracket looking things that ring the bazooka you can get pieces of aluminum duct work and cut them with a pair of metal snips or metal shears. You will have to sand them to keep from cutting your self. To fold the edges get a piece of wood and a rubber mallet or a raw hide mallet, this will keep from denting the metal and use the wood as an edge to hammer the metal to a 90 degree angle. Then to attach the rings to the PVC get machine scews, drill holes slightly smaller than the screw itself in the metal and the PVC. Use Washers and nuts attach. Put one washer on the inside of the metal to keep it from buckling, then put one washer and nut on the inside of the PVC pipe.
It should work, if you have more questions let me know....
Rejoice! For very bad things are about to happen