Eh, 'That Gun' wasn't meant to be an exact replica of the Blade Runner gun. Too many legal problems if it was.
There aren't any actual legit, licensed products of the gun anywhere. Any version of the gun that you can buy are made by fans and given different names to avoid any copyright infringement. Those guns are incredibly accurate, available all over the place, and are made by dozens of different companies. They can get away with it safely because they just don't call them "Blade Runner" guns, because that's the copyright. The "Detective Special" name was one of those made up names to circumvent copyright. There's no copyright or trademark for the shape of the gun. Blade Runner doesn't have the same crazy legal protection that George Lucas put on Star Wars stuff.
Edited by VDantes, 10 February 2016 - 01:01 AM.