3d trees

I was wondering if anyone knew where I could find some 3d trees. I'm not talking about the in-game ones, because those automatically go to the level of the ground. I need some 3d trees that you can place wherever you want, because I am making custom tunnels for one of my current projects. The train is supposed to burrow into a hill, but I don't want a random line of no trees on top of the hill.

If anyone knows where I can find some/wants to make some that would be amazing.