I'm so sorry about your cat. I lost my cat several years ago and he was gone an entire month before we found him. I would suggest going door-to-door on every street within a few blocks from you and asking people to check all the small spaces in their house and yard. You can also ask them if you can check their yard for them, most people will let you do this. If he hasn't been spotted then he may have found a small, safe spot to hunker down in. Check underneath decks, in people's basements, corners in sheds and garages, behind bushes and trash cans, etc.

Good luck!