Most of the magentic phone mounts I found were for the pre-built plastic magnetic ring or magsafe chargers, not for the magnet patches I had around at home. This was made to fit most existing 17mm ball mounts, I use it together with a skadis ball mount.

Putting the P2s on top of a Kallax shelf, it will fit but the front feet will be slightly outside of the plate. These no-screw brackets will extend the shelf slightly so the printer sits securely on the shelf. You can print these for the front or the back of the printer, or both.