I bought my solar charger for about US$20 on eBay. There are many models to choose from, but I chose this one because it had good customer reviews, and suited my purpose of being able to charge my cellphone and my Steampunk iPod
. It also has indicator lights to let you know the charge level, and can output at variety of voltages; from 4.5v to 9 volts.
For my purposes, another thing that is key about this back-up battery and charger is that it has a standard USB attachment, and is capable of powering a USB lamp, of which I've made quite a few, including; my Dieselpunk USB Lamp
, my Steampunk USB mini-lantern
and my Steampunk incandescent USB lamp
One draw back to this device is that it's a bit delicate, and scratches easily. This box comes in handy here, because you can leave the charger in the box, remove the lid, and place it in the sun to charge. (If it's a cloudy day, you can also charge this device through a USB cable connected to your computer).
So while its great to have this device as a back-up battery charger to charge my phone or iPod on the run, it will most likely spend more time sitting on my coffee table powering a homemade lamp;-)