http://www.ebay.com/itm/N-Vertical-Signal-3-light-LEDs-NIB-TMI-22-N-856-/390479801959?pt=Model_RR_Trains&hash=item5aea68ee67
Apparently they are Tomar Ind. and look a far sight better then any other type D's I've seen in N scale. I only need three for the layout, and frankly they will be more for looks then operational necessity. All feed back welcomed!
Then you haven't seen my type D's. Mine are scratch built, and if you don't need them to be functional, they're not that difficult to build. I have actual measurements taken from a UPHS Streamliner that features actual plans for UP's distinctive cantilever signal bridges.
What's wrong with the Tomar's is that they're too big, the mast is too short and too fat, the ladders are wrong and all the LED shtuff on the back just doesn't cut it since it bears absolutely no resemblance to the prototype light housing.
Here's a photo of mine on a modified Traincat UP cantilever bridge.

Here's another photo of mine on one of my scratchbuilt brass bridges at the west end of Echo Yard on the west mainline.

My lamp housing are bit large in order to accommodate a circuit board I'm still planning. Here's some shots of a prototype D-Type signal head on the UP mainline in Morgan, Utah.

Actual measurements of the target are: 57 7/8" tall, 33 7/8" wide, a 16.973" radius curve on top and bottom, the 3ea. 10" dia. (app.) light hole centers are spaced 16 15/16" from top and bottom with the center of the center hole being 12" from the center of both top and bottom holes. Of course, the holes are spaced along the vertical center line of the target which is 16.973" from either edge.
I measured the prototype mast diameter of the signal in Echo Canyon and the best match is stainless hypodermic needle tubing I purchased at
www.smallparts.com. The part # is HTX-20T-60, the ASIN # is B00137POPK and that is for 60" of .036" OD X .026" ID stainless tubing. I figure that diameter plus a coat of paint equals a scale 6" dia., and the ID is big enough for three or four magnet wires when I get around to figuring out the wiring and custom etched/laser-cut-circuit-board to make mine functional.
Here's another photo of a UP signal in Echo Canyon Utah, and shows that on that location on the UP, each signal has the target and mast, a relay cabinet and a special double telegraph/power pole. I assume that other railroads' signals are accompanied by "railroad standard" track furniture, different from road to road.

Hope this provides some useful information about D-Type signal heads and other pertinent information for somebody who wants to build their own, or find the closest commercial equivalent.