Amazon.com has a Belkin Backup Battery Pack for iPod for $19.99 with Free Shipping on orders over $25.
n- n
- The backup pack attaches securely to your iPod with special suction cups to provide 15-20 hours of playing time using standard replaceable batteries. Features: LED indicator to convey battery power; and a secure power switch that prevents accidental on/off powering. Designed for the new 10, 15, 20, 30 and 40 GB iPods.