You can get OEM knock sensors for $55ish shipped on eBay.
Unbolting the sensor is the tough part. Bolting it back on is the easy part. To unbolt it, i had to rig up a tool (made from liiike 3-4 other tools) to get a good position to be able to break the bolt loose. Also, if you have a B14 car, there's a metal brace you will have to take off to get to it. Once you get the bolt loose, go up top and grab the wire for the knock sensor and pull the old sensor up into the engine bay, put the new one on and fish it back down.
All and all, it took me an hour to replace it (45 minutes trying to get that damn bolt loose, 15 to finish it.
Unbolting the sensor is the tough part. Bolting it back on is the easy part. To unbolt it, i had to rig up a tool (made from liiike 3-4 other tools) to get a good position to be able to break the bolt loose. Also, if you have a B14 car, there's a metal brace you will have to take off to get to it. Once you get the bolt loose, go up top and grab the wire for the knock sensor and pull the old sensor up into the engine bay, put the new one on and fish it back down.
All and all, it took me an hour to replace it (45 minutes trying to get that damn bolt loose, 15 to finish it.