I was at the Lego store in Downtown Disney last year and didn't see anything like that... If I had, I wouldn't have had a coffee mug as a souvenier. I would have had one of those...
That is because LEGO's policy is that they will not venture into the WW II or younger time frame of warfare. As such they will not make armor vehciles like these Brickmania – Unofficial Custom Lego Kits nor will thay make realistic gun parts for the minfigs like these BrickArms or the ones in the OP.
As such a "secondary" market has sprung up among the adult fan of lego community to produce that LEGO is unwilling to do.