Floppy disk boxes, specially for 5 1/4 inch disks, go for 50 bucks on eBay, so yeah, this.

Prints fine without supports.

There are a couple of versions provided:

• Base.stl + Lid.stl: A small floppy disk box with a 150mm length (can be printed in small 3D printers like the Ender 3)
• Base - long.stl + Lid - long.stl: A longer floppy disk box with a 250mm length

Also provided is the source file for Fusion 360, which will allow you to set up your own length easily: Go to "Modify" > "Change parameters" and change the "boxWidth" and "numberOfDiscSteps" parameters to fit your needs.

If you want a larger box to fit more disks, or a specific length, let me know!