I have a 2003 Rio Cinco and my catalytic converter did the same thing. So you have 2 options. You can buy a new one (mine is built into the manifold and down pipe as one piece and costs over $450) or you can remove all of the honeycomb material from within and use it that way. If you choose option 2 then you will have a CEL (check engine light) and it will read for an oxygen sensor problem. And your fuel economy will go down. And of course it will not be street legal in states that have a state inspections for smog control.
Because of the age of my car and that it had 145000 miles on it, i chose to just remove the buildup inside. I just currently rolled 168000 miles. And i only lost 2 miles per gallon. So it will work.