There are plenty of people with the required skills and equipment to do this creepy stuff. There were 800 members in the private detectives' assoc. in Balto. MD, and who knows how many non-members. One ex-cop refused to join the association because he was disgusted with their conduct. He said a convicted felon could get a detective's license in MD.
The real advantage to the metal spaces, is that you can drive in, being tracked, and drive out in a different vehicle which doesn’t have any tracking devices.
You might have to crawl under your car and look around rather than just trying to feel for a device. Then, if you do feel for it, at least you'll see visually that you're hitting every nook and cranny.
Have you ever watched the show Burn Notice on USA? It's completed two seasons now. It's about a spy who got burned and has to figure out who and why. Besides the entertainment, the real benefit is the extensive exposure to and explanations for so much creativity in his profession.
Also, what about counterintelligence? What have you done to find out who has been harrassing you for 29 years and how do you know that they actually are? If anyone can get a detective's license in MD, why not you? Also, consider the time spent on this. No one is going to spend 29 years following you themselves, and probably not one year either. They're going to get very bored, get caught up in routine, and get sloppy. That's a weakness to exploit. Also the number of people involved if they've been switching out over all those years. You would find at least one person to talk.