A while back I purchased a 12K Superstone. It arrived in a cardboard box and bubble wrap. That was fine for transport, but I wanted a more protective plastic hone storage box like I had for my Norton and Shapton stones.

Just spotted these Naniwa plastic boxes at a Canadian vendor and ordered the PTC-01 model:
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The Superstone fits perfectly and there is even a space inside for a nagura stone. Good value for just under $7.00 CDN.