Well, the FIRST requirement for a PPC Mac like the G5 is that the drive ahve FireWire connectivity. I believe the Oxford 911 has now been replaced by newer versions. However, I would look to Other World Computung for a proper external drive for a Mac. They have excellent pre-sales support via e-mail.
Look for FireWire drives on their site:
and ask them about bootability. Be sure to tell them in your request that you need it to boot a PowerPC Mac. That might save you having to figure about a chipset config; if it boots a G5, that's what you wanted.
I picked up a Sony external DVD writer for US$5 at a rummage sale for my daughters' PC netbook. I noticed it had a Firewire 400 port but I figured, being Sony it would not be Mac-bootable on our several PPC Macs. Guess what? I was wrong! The model is DRX-820UL-T. If you can find one of those still in someone's inventory, that would be a good thing to have.
I'm really looking to find something cheap on eBay.
Then expect to be disappointed unless you can find that Sony DRX-820UL-T I linked, as I know it's PPC-bootable. Forgot to mention that it's also a dual-layer, so it's no slouch.
Found a few:
Mine didn't come with software but had everything else. I think the only software you need is if you need to burn discs; I doubt Sony inculded Mac drivers for this, but there are free-third-party packages such as PatchBurn that can enable burning.
Don't know about NZ but FireWire cables are pretty cheap in the States. In the local shops, it may be shown as an "IEEE 1394" cable, the industry ID for Apple's FireWire-trademarked connectivity. My Sony has the same FW400 port as my Macs--I think its the 6-pin (bottom port in image):
Didn't get back in time to edit...the image is not the back of the Sony drive, but a generic view of a FW400 port. There is also a smaller connector on the back of the Sony that looks like the 4-pin FW400 port. It's a small-footprint version that was commonly used on smaller peripherals like portable hard drives and cameras. Either a FW40 6-pin to 6-pin or 6-pin to 4-pin would connect the Sony to a PowerBook.
A follow-up on the Sony drive: This morning I connected it to the i7 iMac to see the System Profiler info on it. It's on a USB port at the moment. Here are some pertinent screen shots from Profiler:
First, from the "USB section:
Note the line, "Location ID: 0xfd140000 / 5" --sound like that could indicate an Oxford 914 chipset. NOt sure.
This is the entry for the drive under "Disc Burning":
and, for comparision, the built-in drive:
Looks like the Sony can burn without extra drivers.