I've been quite happy with
http://www.ebay.ca/itm/5V-input-2A-o...-/160725747523 . It keeps my Vox running without a charger for about 12 hours. You do need to purchase the 18650 batteries separately.
I have no idea how long that would keep the Touch charged but I suspect it would be months at several hours reading per month. You charge it using a USB port over night. And of course you can use it to keep just about any USB chargeable device going. (Other than 2 amp devices such as iPad stuff.)