I did research but could only find tumblr and eBay auctions of the same mouse with different company branding. Based on that, I think this could be custom branded merchandise.
There are so many brands with custom floating trinkets in each one.
I have included a picture collage I made with some of the cool ones I found.
Here are more pictures of the mouse we have:
Also Nostalgia Nerd on YouTube shows he also has one of these mice.
These look like they could be a collectable. Anyone have one of these, or a collection?
M and Ms