Quote Originally Posted by EAD15 View Post
Camopaint, California has the most strict smog regulations of all the states. A non-certified catalytic converter would fail the car instantly during the smog check since it isn't approved. That would make the vehicle illegal to drive since you cannot register the vehicle without a passing smog check.

This is why you see "49-state certified" emission parts. Some vehicles are also manufactured 49-state only. Some manufacturers are unable or unwilling to meet the California requirements and sell them as 49-state parts. Also, you cannot legally install a used catalytic converter in California and a new OEM goes for around $1400.

Edit:
To wkshpdad1,
California has a website that details all approved aftermarket cats for each Year/Make/Model of car.

Link

Unfortunately there are NO approved cats for your car. So you simply will not find one.
This thread shows up when google searching for "2009 chevy aveo lt catalytic converter california" so I figured I'd post here:

Link does work wonders, and directed me to WALKERŪ EXHAUST SYSTEMS :: E-Catalog Lookup , where I was able to begin the process of tracking down this part. Probably saved me several hundred dollars.