The physical connector is a standard molex connector with their 0.093" pin configuration. ebay has a pair of plug and receptacle with pins for $10; if you're already placing an order to digikey where you're already paying for shipping, the plug portion is just $2 and pins are 10 cents each. If you prefer, you can print your own with the STLs include in RenixPi on GitHub. 

The electrical specification for the Renix ECU is a very common output  of many ICs: open collector to ground (eg I2C). 

With a pull-up resistor, the (inverted) UART signal can be seen. And along with a transistor and another pull-up resistor, it can be decoded.