get yourself a 3-pack of iPhone 3g universal dock adapters at a mac store
. it'll run you 9 bucks.
then, the awesome part is the tekkeon (i have no commercial relationship to them, just a happy customer!) rechargeable mobile power
unit, purchased for $36.95 on newegg.. basically, its battery pack with a 4,000 mAh capacity (iPhone's battery is 800 mAh i believe) that outputs power to a usb port! perfect for the iphone!
obviously, you need the sync cable, and the iphone itself.
oh, you'll also need some krazy glue, or other adhesive that works on plastic.. might wanna get a sharp knife too..