Hopefully a patch weld can be done on the pipe. Since a rust hole developed in one spot I would be concerned about another hole developing somewhere else. It could be an inexpensive quick fix, but might only be a stop gap solution.

I did a quick search on ebay for "Crossfire Catalytic", and found used, aftermarket, and new OEM for sale. There are certainly lower cost replacement part options. It's the same part for the SLK320. There was even a Magnaflow brand.