if it was as easy as going to a junk yard i'd have no reason to post this, being told no can do saftey regulation,

Junk yard

car-parts.com

or

fordpartsonline.com

It is probably the same as the ones in the Crown Vic and Grand Marq, but Im not certain--the Towncar is rather different in some areas.

you can go to a junkyard, it is legal for safety regs.

the junker just does not want to be held liable should something happen.

you can also order from a dealer.

the bodyshop is full of crap, it is a car made by a US manufacturer, of course they sell parts for it in the US

The airbag you are searching for is available used and it fits 2002 as well. You can also order one from the dealer. The part # is 1W1Z54043B13AAH and it lists for $785. If you are replacing the airbag, you will most likely need other parts as well. Check out this site for more information. It is got a lot of good information (including fault code charts for every vehicle) if you are thinking about doing this yourself
http://airbagsolutions.com/