looking for a pair of 16" steel wheels for My 2006 Mazda6 for the winter

You should check your local junkyard so you won't have to pay shipping, if no luck there check the net

6's are hard because of the factory offset of +60mm. So you'd need a wheel that was a 5x 114.3mm (4.5") bolt circle x at least +50mm offset.
You may also want to check the Tire Rack's winter wheel/tire packages. They are usually pretty good. You can chose one of their pre-made packages, or customize it with the tires you want.