I don't know how well this will work in this situation, but I've drilled a small hole into the end of a rivet, and then you can use a center punch to 'peen' the metal into a rivet bucktail, I've never tried to peen a sensor, so I don't know if it's a soft steel, or aluminum .
Just checked the Hall sensors that I have, (Honeywell 2AV54) and the two pins are magnetic, so they may be a soft steel .