Buy.com has Belkin TunePower for Zune - F8M027 - Works with the 30GB Zune only for $28.95 + free shipping.
TunePower keeps the music playing even when your Zune player’s internal battery is drained. It offers a great solution for long flights, train rides, hikes--any time you want to extend your music and video playtime. A foldout kickstand positions the Zune at the perfect viewing angle, and we include an AC wall charger that works for both your Zune and the TunePower simultaneously. The rechargeable battery is cheaper to maintain and is better for the environment. TunePower also features a protective-case design to prevent damage to the connector from dirt, dust, or impact.
Features
Extends the playtime of your Zune digital media player by 6 to 12 hours
Features a convenient foldout stand for hands-free video viewing
Saves money and the environment with rechargeable battery
Protects your Zune with custom-molded sleeves
Includes AC power adapter
Works with the 30GB Zune only
Belkin TunePower for Zune $28.95 FS 
