Careful if you just buy a new 12 in subwoofer, gotta take alot of things in consideration. Gotta make sure the box size is matched for the driver. Many things to consider.
if you can get a SPEC on the driver itself, you can try to find a sub with matching Q, VAS, etc etc. However, even a little deviation in the specs can reproduce unwanted effects
honestly, yer best bet would be to replace it with an identical 12in driver, unfortunatly that probably means you will actually have to send it in for repair.