Where would I find a rear wheel ABS sensor?

I had my car scanned yesterday to pinpoint the problem that is kicking on the ABS INOP light and it came up with multiple codes pointing to the Left Rear wheel sensor. I have searched online and cant seem to find anywhere that carries this part.

The car is a 97 Z28 with ABS and Traction Control (1 sensor @ each wheel)

Thanks

Before you run out and buy one, be sure the problem isn't magnetic debris clinging to the cogged wheel that the sensor measures.

GM # 10456264

I agree with the above post though, clean the sensor first and see if that solves your problem.