There is only one 24 port card for the MDS 9000 series. We officially refer to it as the 24-port fibre channel switching module (see http://www.cisco.com/en/US/partner/products/ps5990/products_data_sheet0900aecd80446058.html)
or the "24 port line card."
I don't know where the reference to the "port blade" came from but it may just be due to the fact that we may not be consistent in the documentation at various places and that some people also call line cards blades. As I said, there is only one. The Cisco product feature code is DS-X9124. Depending on where you buy from, the storage vendors may have slightly different product feature codes and names.
Ralf