These bulletin boards...sometimes called French Message Boards....can be purchased at most large art and craft stores or discount department stores. They are available in a wide variety of fabric choices and can cost from $5 to $25.
They generally have a sturdy wood frame and are padded...perfect for using u-pins to securely attach bracelets and necklaces.
You can also easily make your own board or recover pre-made boards when worn or to coordinate with your jewelry style.
The crossed ribbons are the perfect place to tuck small signs or tags.
The boards can be placed on an easel or leaned up against a wall or other display item.
For shows, I load the board with jewelry at home and cover the entire thing with kitchen plastic wrap to protect the jewelry during transport.