I never knew that there was such a thing as a magnetic chalk holder until I watched a match that Margarita Fefilova was playing years ago in the pre-Steyer days. She had the clip on her rear pocket, so it was hard to miss when she was down on a shot lol.
When I was playing league I switched from bar chalk to carrying my own (Blue Diamond) because the doofs that were playing league insisted on drilling a hole in the chalk and that made it hard to wipe it over the tip instead. Being ADD, I kept leaving the chalk on the table at the venue since I had never been in the habit of packing it in my case.
So I got a no-name magnetic holder at a tournament booth. First problem, the magnet was not strong enough, kept falling off so I put a very strong coin type magnet under the chalk and although it helped the retention quite a bit, it still falls off once in a while. Second problem, a couple times I could not find it on the floor because it had stuck to a metal chair leg.
But it is still a win because there is only one place, ok... maybe more than one

for it to be since I don't sit it on the table anymore.