While working on model railroad projects this winter (2018/19), I devoted my spare time to developing a line of N scale signals utilizing 3D printing. The first series of signals are now available for purchase on Shapeways and are offered in sets that I refer to as "Turnout Protection Sets". Each set includes 3 signals - 1 double head signal and 2 single head signals to protect both ends of a turnout. These are models of signals and do not have LED's. They're simply nice N scale details that you paint and place on your layout.
Signal models are available in the most common types of North American Class 1 railroad signal head styles, D-Type signals with individual lens shades, D-Type signals with snow hoods, G-Type signals, and Searchlight signals.
Each set goes into print production once ordered from my Shapeways store. The signals sets come unpainted with and feature and easily removable protective packaging and shipping cage.
Shapeways 3D printers can produce and amazing level of detail on these small N scale signals.