Haven't checked lately but I bet Yodobashi still has a dedicated Floppy section.
Alright then, we're upgrading to ZipDisk for added security through obscurity.
Won't help if the finder of the floppies has a Mac. I have a bunch of old floppy disks, but from what I've read online, you can't even hook a USB floppy drive to a Mac anymore. All that code is gone from the OS.
You can install VirtualBox and pass the USB floppy device through to any OS that can read it.
As long as it’s not an M1. I tried recently to read some old CDroms that were formatted for OS9. Not a straightforward process to read those old file systems. And, if you have an M1, you then need to have a w OS that runs on the arm chip. Or, you can use qemu to install os9 in full emulation. What a PITA.
IIRC, really old Macs got extra storage out of a floppy by spinning the disc faster when the read/write heads were on the outer tracks. Made them a wee bit difficult to read on any other hardware.