Herring
Here are files for a BR built Herring ballast hopper drawn full size so scale to suit your model.
They were developments of the earlier Trout hopper but have a slightly longer wheelbase and body with less capacity. They also had a vacuum brake.
Versions with plate and split axleboxes have been drawn.
Appropriate buffers can be found elsewhere in my designs.
Transfers are available from Cambridge Custom Transfers.
Enjoy
Jonny