Here you go: Vulcan Productions Assets. Scroll down until you come to their (freeware) Tree and Grass packs. I don't know about their reflective properties, but trees in particular look rather nice. I doubt these are the only third-party option available, but they seem to be a go-to alternative for those seeking non-vanilla trackside scenery. Worth a look-see in any case.
They are only a few of them (less than 20) and to make a modern landscape You should make a thousands of trees of various type and size as TS doesn't work with SpeedTree or any other similar procedural trees. And then also buches, shrubbery and grass. I have a huge library of trees, quite ready to export them to TS, but I have no interest to work with them. Terrain textures are ugly and there's no ability to plant giant areas with them as TS has no working instances (Asset block doesn't save a significant amount of RAM as it used to be).
