Here's a suggestion that should do what you want.  If you are unable
to obtain some of the 720 kb single hole floppies, you can cover up the
second hole and then format that floppy in an older computer.  I use
a small piece of black plastic electrical tape to cover the unwanted
hole.

Some of the earlier versions of Windows had a provision for formatting
720 kb diskettes.  I would probably go to someone who has an older
computer that has that capability.  I have an old Canon laptop that
I still use for things such as that.

Hal Davis