Ive remixed this great go pro tripod mount and added 4 holes to insert 10X3mm neo magnets. four magnets is enough to hold up my camera but i made the holes deep enough to fit 2 layers to increase the magnets power.
EDIT. The best mount ive made was printed after scaling the model up by .1% The magnets fit much better and camera fit well. I dont know if it was because my plastic shrank more or what so you may need to try and scale for best fit

printed in ugly green at .2mm layer height 20% infill