Nevertheless, I haven't been able to find *any* o2 concentration sensor out there that will fit my needs. If anyone has any clues on where else to look for that component please let me know.
I don't think you are going to find what you want at the price you're willing to pay. We use Oxygen sensors in our R.T.O. system, and they are not cheap.
We have an integrator that is quite knowledgeable with process control. He should be able to assist you with your application, in sourcing your sensors. If it is within your pricing points will depend on your targets.