What do you mean by defused? It got disabled or did it deploy?
Either way, ask your dealer. Anything to do with passenger restraints (seat belt pre-tensioners) and SRS (airbags), the only qualified entity that can restore them safely and reliably is your casa.
If it's the other driver's fault, his insurance should cover it. Otherwise, if your have a comprehensive insurance, check if there's an airbag clause. If so, you can try claiming it as part of the accident. Anyway, the restoration must be performed by a qualified techie, most likely, the car dealer of your brand.