If you are replacing the Woofer look into EV (Electro Voice) models
long as the voice coil was not damaged you could have glued the magnet back on .you just need to glue it so that the voice coil does not rub at all during its travel .
i done that once before .i have also replaced the foam surround on a set of cerwin vega`s ,same deal there .you need make sure the coil does not rub .
i would use a 2 part clear epoxy to glue the magnet,just a thin coat then let it sit on its face for 24 hours.