O2 Sensor for RB20DET

[dmaestro]

My O2 sensor on my RB20 is toast. Anyone know where I can get a OEM/Universal O2 sensor that will work for my engine? I looked at my friends 1989 300ZX and it has a 4 wire w/4 prong O2 sensor, where as mine is 3 wire/3 prong.

Any ideas?

Thanks