The r4i 3ds gold + came and it unknowingly came with a magnet. Heres the kicker, its like 1/2th the size of my nail...They don't have to be insanely strong. A few stacked above the sensor should do it. Good luck
It does stick to metal areas pretty well though, its sticking to the front of my soundbar and bottom of my monitor pretty easilly...
Hopefully this one will work Just waiting on the 3DS now.