Hi... I'm not sure if your son is verbal or not, but my three year old isn't so we got him a RoadID tag for his shoe. It has his name, date of birth and phone numbers for me and his grandmother. It's helped a little with the fear in public. Your local police department might have a tracking bracelet that you can get for your kids too. They're free if you register. But check with your police department to determine if they participate. Your fear is normal. Especially if they like to wander. You aren't alone. Good luck!

I worry about wandering every day of my life. My 7 yr.old is non-verbal autistic, is a runner, and has no sense of danger. I hate feeling helpless in situations like these.

These fears are normal. Our loved ones on the spectrum wander much more often than others' kids. I used to worry I went overboard with safety but one of my kids is very... unsafe on his own so it's a necessary evil for my family. I would advise making the home environment as secure as possible... GE door/window alarms, double keyed deadbolt locks on the door, fully fenced yard if you can. When in public it depends what you're comfortable with and how much of a wandering issue exists. Backpacks can be easily modified to help with safety. ID tags with name and info. You can get temporary tattoos made for identity purposes if they were to get out or away from anyone. All of these are small precautions that could save a life.
You are not alone. I worry and prepare. You could almost say it's a hobby of mine. Even with all the precautions I take my youngest jumped in a pond on a 'safe' outing mothers day weekend and I had to jump in after him and fish him out. Did I mention CPR and first aid? Just in case. Paying off for me.