Man, I was looking for the same thing last month and it was trickier than expected. There's a decent-sized online fanbase for 'Dogboy', but tracking down the official stuff can be a bit of a maze. The author, Victor Kelleher, is Australian, and a lot of his titles seem to be published by Penguin Books Australia, at least originally. That's probably your best starting point.
I'd check major retailers like Audible and Amazon for the audiobook, but honestly, your mileage may vary. I found an ebook version on Google Play Books in some regions, but it wasn't available where I was. Libraries could be a solid bet through OverDrive or Libby, especially if you're okay with the wait. Sometimes these older YA novels from the 90s aren't given the big digital re-release treatment, so you might have to hunt a bit. I ended up finding a used paperback copy online, which honestly added to the retro charm of reading it.