A few years ago I picked up a couple of exact copies of the OEM knock sensor from O'Reillys for ~$40 each however that same part may not still be available.
Rockauto sells an NTK brand sensor for ~$95.
NTK IME makes reliable products.
Another busted Knock sensor connector
Recently found the #2 Knock sensor connector to have snapped off, the connector was just loosely hanging on the knock sensor, the tip off was an intermiitent loss of power. So the sensor connector piece was stuck inside the harness connector and after a few tries was unable to remove the stuck...
forum.ih8mud.com
Rockauto sells an NTK brand sensor for ~$95.
NTK IME makes reliable products.