Special thanks to Leo Knijnenburg and Ko Maljaars of the Netherlands for doing fabulous research circa 2013 on replacement EFI sensors for the CX500 and CX650 Honda Turbos!
In addition to my upgrade harness, you will need to source a Suzuki (Denso) Sensor.
The sensors below will replace both the Honda Pb (BLUE plug) plug sensor and the Honda P1 (GREEN plug) sensor:
Suzuki part #15620-35F00.
These are readily available new and used from various suppliers. This sensor has been extensively tested on Honda Turbos including my own CX500 Turbo. I generally buy used ones on EBAY.
The Toyota sensors mentioned by Leo and Ko are also Denso products and work with my harness as well.
Toyota: #89420-16080
Toyota #89420-02010
These should work well, since they have essentially identical specs compared to the Suzuki sensor. They do cost more and have not been as extensively tested as the Suzuki sensor.
The Honda Pb (BLUE plug) and P1 (GREEN plug) sensors are actually the same except for plug colors, wire colors and harness length. Because of these details, they are mot interchangeable.
The full discussion is here: