Arduino Project - Social distance detector

I am trying to make a social distance detector for a project of mine. There are many projects online about this, but none of them are the right ones. I’m trying to make a thing that attaches to a lanyard. My original plan was when a PIR sensor detected a human, it would trigger the ultrasonic sensor into measuring the distance between the lanyard and the human. The problem is, the PIR sensor was always displaying “high”, and after doing some research, a PIR sensor can be only stationary. I am wondering if there are other easy and cheap options other than PIR sensors that can detect humans accurately? Thanks!

did you see ultrasonic HC-sr04 sensor with 2cm to 400cm range and with 3mm accuracy?
this is enough?
datasheet
arduino project of this sensor

smsebna:
did you see ultrasonic HC-sr04 sensor with 2cm to 400cm range and with 3mm accuracy?
this is enough?

…but has to be pointing at the object you want to measure the distance to.

Are you talking about buying a more accurate alternative than PIR sensors?