I'm sorry that you don't realized before about the insert foam! :(
The images in the shop are 3D renders only as illustration, not photos.
I know that some of my customers, made the insert easily, cutting two pieces of foam, in the shape of the internal part of the bottom half, and covered it with felt or other similar fabric.
The bottom half of the ring box, has an internal flange, so if you cut the foam with appropriate height, the pressure of the foam is enough to firm them, but if needed, you can use a bit of hot glue, as well.
Hope it helps!