Here's a quick and simple way to make a Zune AC Adapter without buying the actual one from Microsoft. Basically, you manipulate an existing 5 Volt AC Adapter to support a USB plug. It's important to find the right AC Adapter and to wire it to the right pinouts in a USB plug. I'll cover all of that.
What's great about this is that it's actually a universal USB charger since it's equivalent to existing USB ports. If your MP3 player requires a USB cable to charge the battery, then this will certainly work with it.
I recently found out that this only works with the First Generation Zunes, like the Fat 30gb and Fat 80gb Zunes.
Do not attempt to try this with the 2nd Gen slim model Zunes (4gb, 8gb, 30gb, 80gb 120 gb slim zunes).
I found out that Microsoft designed the 2nd Gen Zunes to be incompatible with the third-party AC Adapters. Even the Official AC Adapters that were designed for the 1st Gen Zunes are incompatible with the 2nd Gen Zunes.