I'm trying to locate a wiring harness for my new stereo that I want to install into my 2000 Chevy Cavalier, but I'm having a difficult time find one.
Does anyone know of a after market harness that would fit my car?
Best Buy will have one. Go to their stereo installation shop, which is usually accessed around the side of the building. They will have the harness adapter which will plug directly from your new stereo to the existing wire harness without the need for modification, so you can reinstall your old stereo if you ever sell the car. They will also have professional facial plates for a clean install. Both of these will make installation very easy.
Go to Crutchfield.com under Car Audio, Build your System, click find what fits your car. Enter your car info and then click on the Parts & Tools to install a receiver, then Factory System Adapters. There will be a list of what fits your car.
Note you may need more than an adapter that simply connects the wires to the wires. In 2000 GM started running the door chime, and other warning sounds (seatbelt, low fuel, low oil pressure etc) through the radio. If you are installing an aftermarket radio in one these vehicles you will need an integration adapter to keep the chimes and safety warnings.
Below is an example of what you need. You didn't provide enough information in your question for me to tell you the exact model so you will need to go to the site and look up the correct one for your vehicle.