I am a big fan of MOW equipment. Since there is not much out there I have made several pieces myself. To my knowledge no one makes an actual ballast hopper.
Here are two cars that provided me inspiration.....
Here is my latest MOW creation...
I made the decals except for the UP herald and the black freight car data placards. I topped the car off with road ballast from Dennis Brennan. It is a fantasy car, but I am very happy with the finished product!