Is there a magnet that is made to go on a Hed 3 wheel?
Depends on the computer you use. I use the Avocet, and just glued a ring onto the hub.
The computer is some goofy Trek 'puter.
You might be able to do similar with a single magnet. Try electrical tape first, and bind it to the hub, then move the sensor down the fork to pick it up. If it works, then try gluing it. With the magnet so close to the axle, it won’t cause imbalance problems.
go to a radio shack and buy a small ceramic magnet. then just super glue it to your wheel. the ceramic magnets are insanely strong so you can buy a really small one. I have done this on my spoked wheel too
I’ve used HED3 wheels for racing and training for many years. I go to the local hardware store and buy a few magnets at 25 cents each. They are about 1/2 inch in diameter and 1/8 inch thick. They reach the pickup if you turn the pickup in slightly. While at the hardware store buy a small bit of double sided tape to tape the magnet to the rim. it won’t hurt the rim and I’ve never lost a magnet either.