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