I had a Sun Ray In-Line probe on my DFX. No danger of ever leaving it behind in the woods! When I got my new machine I had to buy a hand held probe. I figured there was a good chance I would leave it behind at a site some day. Here's my version of a probe tether.
I picked up one of those retractable key ring holders at the Home "Despot" and attached my probe to it. Simply connected the key ring holder (#2) to one of those adjustable Velcro straps (#3) that you get when you buy a coil of rope at the hardware store. It already comes with that handy plastic connector. Just adjust the the strap to fit snugly around the probe. It wasn't even really needed, but I rolled an O-ring (#4) up on the probe to keep it from sliding out of the strap. Finally I just clip the key ring holder to the D-ring (#1) on my finds belt.
The key ring chain will extend out 24 inches. Unless you play Center for the Boston Celtics, that 2 feet of chain is more than enough for you to extend your arm out full length to pin point your target in the hole.
The probe stays in the pouch when not in use. I like that the chain just retracts back in and you don't have a any springy coiled headphone type wire exposed to getting caught up in the brush when you are out in the woods. It was about $6 for the retractable key chain, the other stuff I had lying around. I got to use the rig once out in the field before the endless snow storms arrived and it worked fine.