I've been play the last chapter of this campaign over and over again to get him to appear ever since i read him on the wikia. I know it's going to take awhile, because he only has a 5 percent spawning rate.
I saw this model without using any commands or something like that. He was laying on the floor at the left once you get out of the safe room in the last chapter of dead center. It was *Chai-the-Fox first time playing and he was the one finding him, and I was like "... WHAT... D-DUDE... T-THIS WASN'T HERE BEFORE..."