Take the old one off, take a long piece of rebar and ram it through the cat several times. Make sure you get all of the loose pieces out and then put it back on.

 

If memory serves me correctly, the pre cat and exhaust manifold come as one part, so you'd have to get a replacement part w both.

See

https://www.rockauto.com/en/catalog/saturn,2002,sl+sedan,1.9l+l4+sohc,1388549,exhaust+ &+emission,catalytic+converter,5808



From Rock Auto

Could roll the dice and pull a junkyard piece.

Indeed you could hollow it out if you don't have to pass emissions testing, but based on how you asked the question, I'm thinking you do need to pass emissions.

 

That's a hell of a design. I had no idea it was like that. No way that a piece of rebar will fix that! And like derf stated, if you have to pass emissions testing, a punched out cat con will NOT pass. Do what you gotta do, but I'd be checking the salvage yards.