Saw these trees and they seem cheaper than elsewhere (feel free to put up links if you find otherwise!). Suntek has a good variety of these, and their bulk sets seem to be a good deal.
I'm not a model train geek, but I am a D&D geek, and am using these (and others) w/minis. Just have to attach bases!
A pack of 20pcs landscape model trees
Perfect to enhance the appearance of your model landscape with a touch of greenery
Color: Green and brown
Made of plastic cement
Height: Approx. 3 inch / 7 cm ( root included)
Width: Approx. 2 inch / 5.5cm
20 pcs model trees