Hi,
Do you have any PPC/Intel Macs capable of running Mac OS X 10.4.x or below?
If you do, you could get yourself a USB ZIP drive (alternatively, you could get an internal ATAPI ZIP drive for your B&W G3, if it doesn't already have one). With such a setup, you should be able to use Disk Utility to format the ZIP disks for use in the Plus (with the added benefit of the disk behaving like a fixed disk; as such, it will not auto-eject at shutdown or restart, which is nice if you're going to be using it as a semi-permanent boot disk).
One caveat you should be aware of, however: the Mac OS 9 disk drivers that Disk Utility installs on the disk may not be compatible with the Plus (upon insertion of an incompatible disk, the computer will display a dialog, complaining that you need a 68040 or PPC machine to mount a volume over 4 GB; I don't know why this is, but it obviously means that it's incompatible somehow). If you're faced with such a disk, you should find yourself a copy of the patched Apple HD SC Setup v. 7.3.5 and run the disk through that (on a classic Mac, of course) before you use it on your OS X machine; it should still work fine on OS X even if it's been formatted on the Plus (I've confirmed that a disk formatted on a Classic II will function properly on OS X; the Plus may be slightly different, but it should still work).
I hope this helps :b&w:
Please feel free to PM any other ZIP-related questions.
c