Mineral and Salt Blocks
Many Pet Shops stock mineral blocks and salt blocks for mice. These are not really necessary for the mouse's well being.
Cardboard Tubes
Old cardboard tubes or toilet roll tubes can be provided for the mouse and it will enjoy using it as something to climb through, on or nest in as well as chewing it to pieces.
Tubes and See-Saws
There are a variety of plastic or wooden tubes and see-saws sold in Pet Shops for small animals which mice enjoy.
Wood Gnaws
Wood gnaws are available in Pet Shops or you can provide your own by supplying the mouse with a piece of apple branch. These provide the mouse with something on which to gnaw in order to keep its teeth trim.