It's the second building on the left in the foreground.
I needed a break from the Gorre engine house, so I threw together a similar sign in The Gimp.
I went for a 1950s look, because I figured that was when Ray Stantz grew up. The sign in the movie looks a bit more 1930s, with a fatter version of Mr. Stay Puft. The slogan, "Stay Puft, Even When Toasted!" was apparently part of the original script, but it was cut out, and only appears in the film on the matte painting.
I'm tucking this away for future use.