I don't think a 2012 Passat is going to have in-seat airbags, but it's a good thing to be cautious of. Every one I've seen has had a label on the seat indicating one is in there, so it's worth a look.
I've bought seat covers from Seat Covers Unlimited and one or two others. I suspect they all outsource the actual production because several of these vendors have different Web sites, but nearly identical "configurator" tools and fabric/style options.
We've also bought generics off Amazon. They never fit as well as the custom-cut versions and take longer to install but the quality is actually not that bad and the price is insanely low. I have custom covers in my RAM and my wife has generics in her Pacifica. Mine look a bit nicer for sure, but cost like $950 while hers cost <$200. YMMV...