The "serial" bit of RS-232 serial only requires two wires as described. The RS-232 bit is a standard that describes a wiring interface that was used between computers and modems and has been hijacked for virtually anything you can think of since.

The standard specifies wiring and connectors that provide various handshake and status signalling to allow communication management in the original context for which it was designed. For the vast majority of applications derivitaves of RS-232 are used for now the handshaking ans status are almost completely irrelevant. For your application it has degenerated to a single direction signal that only requires two wires.

The reason you can find nothing on two wire RS-232 is because there is no such animal. However, to use your transducer you can find a wiring diagram for the 9 pin connector often used for serial ports these days and connect signal to the serial in line on the connector. Common of course goes to common. Once you have done that you can use your serial modules to configure the port according to the specification you already have (8 bits,one stop, one start, 1200 baud), make sure you turn off handshake, and away you go.