No one else has any technical information on these speakers either, so I’ll be surprised if anyone can give you any recommendations. It’s best just to repair the ones you have with one of those surround kits, unless the voice coils are blown or something. If you don’t want to do that, then just use a multimeter to determine the nominal impedance and pick a speaker from a vendor that’s designed for the size of the cabinet.
Regards,
Wayne A. Pflughaupt