If you can figure out a way to downgrade, I would love to hear it! I had the same thought, but the only other iTunes dmg I could find is on my iLife 6 disk. This is iTunes 6, and plugging the iPod into this version prompts the message that the iPod needs iTunes 7 or later to run.
I ran across a link from Apple for a version of iTunes 8. It isn't readily posted in an intuitive place, but I have it bookmarked. I'm not sure if it will work, but it's downloading at the moment. I found a supposed iTunes 8 dmg on Rapidshare last night... I know... that's bad, but whatever... its supposed to be free software upgrades on iTunes. It's not supposed to ruin your hardware's functionality. Ethical dilemma aside, after downloading this iTunes downgrade and trying to install, I was given the prompt, "This version of iTunes is old," and it would not proceed past that point. It was the most condescending prompt my computer has ever given me, which gave me a chuckle, but didn't solve my current issue.
I will post the link if this downgrade does indeed happen to work.