I bought my track lighting at HD. Unfortunately, the particular model is now a discontinued item. But they did market a replacement, so go in and look.
The cobalt blue paint for the sky is easy, as they mix it for you right there in the store. I blended my sky with white as I got closer to the horizon. Its a little tricky to get right, but you can always paint over it if you don't like your efforts.
Here is another thought: Blue Christmas LED strings. Put them down low behind your buildings and give yourself a gap between the back/sides of the layout and the wall to hide them just below the tops of the hills. Kill the main lights in the room and light the strings for a neat night effect. Buy a string or 2 as a trial. If you do not like it, use them next Christmas on the house!
Chris