If aftermarket is ok, there are a few sources, eg. https://www.ebay.com/itm/EVOFLOW-FERRARI-348-Mondial-T-HIGH-FLOW-CATS-CATALYTIC-CONVERTERS-/252682733478 This is a cheaper non oem version, looks like the correct part and the maker is credible, would check directly with the supplier to confirm the fit is OEM like. https://www.ebay.com/itm/Catalytic-Converter-DEC-Converters-FE4305-fits-1989-Ferrari-Mondial-t-3-4L-V8/152806211900?fits=Make:Ferrari|Model:Mondial+t&epid=112703208&hash=item2393f5c13c:g:1lUAAOSwK~RaHXpl Fab Speed also offers a recoring service for the OEM cat if that's the way to go. http://www.fabspeed.com/348/ As for OEM, the usual parts places like Eurospares carry them. Red Bay spares may have some decent used ones as well.
