Print the parts preferably in ABS, PCTG etc as the nut and guide screw are press fit.

Hardware needed for one:
1 x Locking bolt M6 (I used 60mm) with rounded top
1 x M6 shallow nut, 3mm thick
2 x small M6 washers
1 x M3 hex with long unthreaded part
1 x Spring (mine was od 9mm id 7,5mm and length 36mm)
1 x Counter sunk magnet 25mm
Optional: small pieces of heat shrink

Assembly:
Print the parts with your normal settings.
Press fit the nut into the top piece.
Cut away the threaded part of the M3 hex screw and press fit into the recessed part of the top piece.
Put one M6 washer onto the locking bolt then the spring and the second washer on top.

If needed drill out the 3mm hole in the bottom part to have the M3 screw sliding easily.

For the locking bolt to move freely on the magnet you need to grind away the numbers on the rounded face with a dremel or similar.

Assemble the two pieces and thread the parts onto the bolt. The triple does not have a guide hole so it can be freely adjusted to suite a PCB or similar.

You can adjust the clamping tension with how far down you thread the parts, the whole thing slides easier if you have the bottom part on the non-threaded part.

If you want you can put a bit of heat shrink on the ends.

This is a simple setup and you can easily design new arms etc for your needs.

Took some inspiration from @YuriRage_623017 https://www.printables.com/model/408879-magnetic-helping-hands but ended up designing my own.