Bob,
the seats in my car have metal vents. The oval frame is chromed for sure and probably the wire mesh also. Like most parts made by M-B in the sixties they are not simple but are assembled from 3 pieces (see picture). If it is the wire mesh that's cracked then you should be able to replace it with a new one. Mesh fabric is available in stainless steel from laboratory supply companies, for example.
I have seen them on eBay and you might want to send an email through the web site to vendors who routinely sell Pagoda parts, for example, "jonp821" and "vespa113", perhaps they have a pair.
Download Attachment: Seat_vent.jpg74.07 KB
Alfred
1966 blue 230SL automatic