the contour & focus cannot interchange airbags...you will have to get one specific to the wheel.
About $400-600 new, or maybe a couple hundred or less on ebay if you're lucky & can find one used. To be on the safe side, I'd also get the module that goes w/ the bag rather than trying to use the existing one (you may have to anyway)...
if you're on the daring side you can get a cover instead of a bag...
www.hicksairbagcovers.comit looks like an airbag...just paint to match $50-75