What Mofi said.
I would shield the motor. The cartridge is a good one. Shielding may take some time and effort to install but would be cheaper than spending on a new cartridge that will at best be as good as the one you've got. I suggest you get sheet of mu metal and cut it so as to fit under the platter mat. It needs to be grounded, but contact with the underlying platter would likely by itself be sufficient to do that, in that case. Otherwise, lift the platter off and see if you can affix some mu metal over the motor. Then ground the shield. You could even try just a thin sheet of ordinary copper from a hardware store.
I would shield the motor. The cartridge is a good one. Shielding may take some time and effort to install but would be cheaper than spending on a new cartridge that will at best be as good as the one you've got. I suggest you get sheet of mu metal and cut it so as to fit under the platter mat. It needs to be grounded, but contact with the underlying platter would likely by itself be sufficient to do that, in that case. Otherwise, lift the platter off and see if you can affix some mu metal over the motor. Then ground the shield. You could even try just a thin sheet of ordinary copper from a hardware store.