Thanks for the comments. I suppose I will call Apple when I have the chance. I'm a bit doubtful that almost 4 years after production, they still have CDs for the machine though.
The problem is that any OS 9 I try, whether on internal or external hard drive, or on CD-ROM, fails to boot (although OS X readily boots from either). This is the basic CD-ROM drive model, but the built-in CD-ROM is broken, so I've been using an MBP in Firewire Disk mode as an external CD-ROM (which, as I say, works, at least for OS X 10.3 and 10.4).