Magnaflow now offers replacement catalytic converters with exhaust manifolds and are available thru Marken Performance as a special order (even though it's not on Marken's web price list, it still may be in stock @ Magnaflow).  

Most of these are a 1 piece unit just like your OEM cars.  With increased demands on emissions, many OE car manufacturers are going this route calling these pre-cats which are directly attached to and part of the exhaust manifold.  These manufacturers also have main catalytic converters downstream in the exhaust.  Example: my car is a V6 front wheel drive and has 2 pre-cat/exhaust manifolds (front & rear) as well as 1 main rear regular catalytic converter half way down the car.  Magnaflow now offers these for most car manufacturers.  

For more info from a Video by Magnaflow: ClickMe 

To Search for all catalytic converters: ClickHere  

    Select 49 State (for Canada) OR California.  Then enter your Make, Model & Year