2004 Jeep Liberty Catalytic Converter

I took my car in for a metal rattling noise. I got a call back from my mechanic saying that the guy who fixed my heads dropped a bolt down the head (?) And it made it's way to the catalytic converter. They say that I need a new catalytic converter and they have to get one from a dealership. Total cost will be about $1800. I want to know if it's possible for a bolt to travel all the way to the catalytic converter and also where I can look for a cheaper catalytic converter.