I've never seen either a conversion kit, or 3rd party barrels for the Taurus Mil Pro.
Most conversions require a barrel which requires correct recoil springs. Going from .40 S&W to 9mm might also require a new extractor. Since the frames are marked for caliber, you may have to purchase a correct slide.
Again, the point is will made... as cheap as Taurus prices their guns, a second gun would probably be as cheap as a conversion.