When I purchased my GoPro, it came affixed to a good quality plastic baseplate. These baseplates shouldn’t be thrown away as they can be made into useful additional free mounts.
There are many ideas on the Internet and YouTube explaining how to make many possible mounts. I never saw a “How to…” video for a magnetic mount so decided to make one for myself.
Magnetic Mount Supplies
I purchased my magnet from Guy’s Magnets. After looking through the wide range of magnets he has available, I saw a 30mm by 15mm by 5mm High Grade Neodymium block with a 16kg hold and 2kg slide strength. Because this mount will often be placed in the vertical position, the slide strength was important to me, 2kgs seemed enough for a GoPro.
The glue used is that found in a standard glue gun. You can use anything to cut the baseplate such as a Coping Saw and file. I am lucky enough to have a Dremel and so used that for this project.
As this is a magnetic mount, I would advise that you DO NOT store it near your GoPro as it could affect the SD card or even perhaps the electronics within your device. I think it is worth mentioning that I also used a 3-Way GoPro Mount to ensure the magnet was some distance away from the base.