disable passenger airbag on Vauxhall Zafira

Question

How can I safely turn off the front passenger airbag in a Vauxhall (Opel) Zafira MkII (2005-), so that a child seat can be fitted? This is commonly done with a key in the glove box or switch on dashboard end in other makes of car.

I have found and discarded the following ideas:

1. Discard existing car seats and buy special expensive Vauxhall seats fitted with airbag transponder (discarded as not available online nor at my local dealer).
2. Persuade your local dealer to disable it electronically. Some people online seem have succeeded in this, albeit expensively, but apparently most have not, due to "safety concerns" which the mythical seat mentioned in 1. avoids somehow. (my dealer will not do it, discarded as apparently impossible).
3. Trigger the airbag (discarded as unsafe and stupid).
4. Several apparently untested suggestions to either disconnect or remove the airbag manually (discarded so far as either impractical, ineffective, unsafe, illegal or combination).

Any practical suggestions would be very welcome.

Answer 1

The thing about airbags is that they make cars safer for the occupants (mostly), this is generally a good thing and a net positive. The trouble is that it then allows car manufacturers to build slightly less safe cars that and still pass crash tests, design regulations and other safety regulations. So the reason that some cars don't have an airbag disabling key in the glove box or elsewhere could be because disabling the airbag would put the car in a state where it would not pass safety regulations so the manufacturer (or relevant government body) decided it would never be a valid option. Of course, another reason is to not fit a disabling key is that its cheaper not to.
This is just a general statement about airbags and the way cars are designed, manufactured and tested these days, it's not specific to the Vauxhall (Opel) Zafira MkII.

Assuming you are aware of all the pros and cons of disabling the airbag (I've only broadly outlined a basic safety issue, there is more than that to consider) your options are very limited because unfortunately you've discarded pretty much everything that is likely to be effective. But I do agree with most of your reasons for discarding them.
Your best bet is to find another dealer that will disable it for you.
Or try to find someone who isn't a dealer but has the equipment to do it for you. Aftermarket shops are often familiar with the concept because they replace airbag steeringwheels with 'race' ones.
As William Cline has suggested in a comment, you could try to source an appropriate aftermarket OBD system that will allow you to turn the airbag off yourself electronically.
Disconnecting the airbag is still an option, it should be a relatively simple task especially if you can get hold of a decent mechanics manual for the car. There are at least 2 Cons to doing this though:

1. Disconnecting will definitely cause a 'fault' to be registered somewhere in the cars electronics and it will almost certainly cause a warning light on the dash to be illuminated. In more modern cars, often once an Airbag fault is recorded the warning won't be turned off until a dealer resets the 'computer' so even if you plug the airbag back in again, the warning light will likely remain on.
2. You probably won't know 100% for certain that you have correctly disconnected the airbag and it's not something easily tested.