Get a PVC pipe, glue some sticks on the bottom, paint it black, done.
The result will be better than if you pepped it, I can almost guarantee it. Pepakura is bad for weapons because it's paper, and it's made to end up as a solid box, whereas armor ends up with no closed areas. There's a front and a back. Its third dimension is in curves, but there are no closed areas. This lets you reinforce it.
In agreement with the others, mod a Nerf Titan or get someone to make you a replica.