If you are on a budget you can turn pretty much any wooden box into a pastel box that can be closed when full of pastels by adding some removable panels with rotating framing turn buttons that hold them in place and some foam padding. My last one cost me under $15 complete and has been working well for 3 years.
I have built them from on sale $9-$15 wooden oil paint cases like the link below but cheaper still, using small cardboard pastel boxes to divide up the open top half with 1/8" "Masonite" hardboard or 1/8" or 1/4" birch plywood for the retaining covers. You can also use strips of thin wood to further divide the top or the bottom. Add foam as needed to protect the pastels so they don't rattle. Cut the hardboard so it just fits inside the box frame, flush with the top edges. Stagger the turn buttons so they are not opposite each other on each half of the box, then cut a little notch on the other side so the lid will close fully. If the frame of the box doesn't allow the top to lay flat, they can easily be modified by removing any tabs that prevent that.