This is my solution for mounting vive trackers on human body.

Wide belt was taken from here https://www.aliexpress.com/item/33039087281.html
(one piece used for hip belt and another one is cut in half for using on both legs)
or you can use ordinary flexible belt from a clothing store.

And narrow bands to keep trackers in place are just cheap elastic bands from a hardware store.
The length of the elastic should be 50 cm (19.7 inch). And the two ends are sewn together on the back.