Chevy HHR Stereo Install

Can anyone tell me where to find a wiring harness that will work with a 2006 Chevy HHR, or failing that, find a wiring diagram?
I purchased a harness from a local installer, but the connector is not
correct. The current factory stereo has two small connectors, one with 16-pins the other with 14-pins. Presumably this is a GM/Chev connector, and not specific to the HHR.
Any insight would be greatly appreciated.

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