Tabletop Terrain : Offers 3D-printed sets with varying quality levels (Normal vs. High Detail). You can purchase the "Game Only" for around $30–$60 or a full set with a custom box for up to $100.
Certain custom designers have listed premium sets on platforms like Shapeways , though these can cost upwards of $300 due to the complexity of the materials.
Etsy (TabletopTerrain3D) : A highly-rated "Star Seller" offering similar 3D-printed models inspired by the books. :