Airbag and control module

I have a 06 Malibu Maxx that was in a collision. I have the body work completed, but the shop says they can’t do the airbag and srs control module/ computer. Where can I buy these other than dealer? online sources?

You need a shop other than an auto body shop to work on the car’s electronics. A proposal to buy computer modules is not the first step in repairing those systems. Find the right kind of shop for these repairs. It may, in the end, be a dealer’s repair facility.
If the insurance is covering the body repairs, they, also, will cover the electronics’ repairs.