Haha it's just a replica to display or use for cosplay. You could pretty much use any that's made for a baseball. I've seen acrylic ones you can get off of amazon. They do come in packs of 10 but you could probably find single ones if you search about.
This turned into a DIY project after the product wasn't ideally compatible for what I wanted to use it for. I didn't want to pay the prices I was seeing online for ready to use cases so i bought this baseball bat display case for $50 from Amazon. It turned out that it had the builtin baseball bat holder on the base and then you slide the cover on, so when I got it I was kind of "WTF this is going to push everything off", and also I would have to place the Amiibos on the sliding lid, so I got a dremel and cut the bat holder, drilled 4 small holes for the light insert point (and worked up... acrylic) and stuck the amiibos down with that credit card glue (reusable "Glue Dots"). Gigantic pain in the butt, but honestly the pics dont look nearly as nice as it does... reminds me of a museum display and god I like looking at Amiibos :) https://www.amazon.com/OnDisplay-Deluxe-UV-Protected-Baseball-Display/dp/B071R35GL5/ref=sr_1_1?ie=UTF8&qid=1498800860&sr=8-1&keywords=ondisplay+acrylic+baseball
HERE is a better closeup picture https://imgur.com/a/EX5Xn
Have you tried these bats and don't like them? I think they are great. You can of course add grip tape if you like. The only downside about these in my opinion is that they will eventually warp if out in the hot sun a day a lot. But I think that's pretty much unavoidable with any plastic bat. https://www.amazon.com/Easton-Pro-Stix-Training-Set/dp/B001Q9RUFW/
I have this one and I like it. Five spaces per row for each division, plus two extra rows for when they change names or other random balls I have.