This is coming from a former Transport Canada - Accident/Defect Investigator (my father). It is not illegal to disable an air bag, and most garages have the ability to do so. However, with the liability behind it all, there are not many licensed mechanics that will do this for you. I know you can sign a waiver and all, but things can still be taken to court. Thus....most shops will not do this for you, I'm not saying no one will, but you may have to look around for a while.
The exception is this though....they can sell you the parts, and may even tell you how to do it. This way, they didn't do the work, and as such cannot be held liable for it.