Newegg has a small rechargeable power supply that works with all versions of iPhone and all iPods with the 30-pin dock connectors. The Miccus ChargeBlock CBFI-01 has an 800 mAh rechargeable lithium ion battery that lasts 500+ charges. It charges with the included mini-USB cord, and outputs 5V/+/-0.25V. It has automatic on/off charging that prevents overcharging your device battery. The Miccus ChargeBlock has LEDs that indicate charging status and shows the amount of power it has remaining. The Miccus ChargeBlock CBFI-01 is $19.99, with free shipping in the continental US.