I have seen a number of 190s with exhaust failures you describe. They all had poor supports at the back of the tranny.
I would try and buy Ebersbacher exhaust from a supplier or definitely consider timevalve (as mentioed above). I'm sure their product would never fracture; being stainless steel. And as stated above I too have seen numerous systems over ten years old that still shined like new.
As to the catalyst we would TIG weld it back together if it were just fractured. The aftermarket versions are POS compared to OE, but OE is probably around $1700.
Bosch Master, ASE Master, L1
33 years MB technician