Best part is the tan version is one of the basic options, no extra charge Then there's the tactical version, where the slide is also tan and comes with a threaded barrel and night sights, costs a fair bit more though.
Yeah that's what I saw when I searched for those asking. I paid something like $10 when the NZ military was clearing out surplus. Outside of surplus and used they're going to be expensive, full price modern mask. It's funny the Russian engineers use them in BF3, but this mask is only used in non combat roles because corrosive chemical weapons eat the rubber one it.
PX4 looks similar, but mine is a S&W M&P9. Main differences are in the location (or lack of) safety and takedown levers, and the back end of the slide, both do have a very ergonomic look. The mask I got for cheap, like $10 many years ago. Now I see it costs several hundred