dude, i hate to do this, but what about your truck and the coolant leak and the oil leak? how does that extra coolant burnin affect the environment?
good ol' mother earth was here long before we were and has survived much worse than we can dish out, so relax and get rid of that power robbing worthless catalytic converter
and to answer the question, just go to a parts store or exhaust shop and get a straight piece of pipe that would replace the cat and stick it in its place