Is it possible to make a usb charger to power multiple devices?
A 5 Volt power supply of whatever rating suits plus some USB port hardware is the main requirement. 

Just increasing the power feed to a cheap USB hub is probably the cheapest easiest way. Some existing current limiting hardware MAY need to be bypassed. 

5V, 5A should be ample. As you are located on Nowhere, OK you should have no problem picking one up locally. 



ADDED

Here's a bargain powered USB hub on ebay UK. 4 GBP for a 7 port hub wit power supply. Power supply is rated at 1A, 5V, so

ebay UK 5A 5.5V psu GBP7.80 buy now - from Hong Kong BUT free economy delivery.

5V 5A GBP8.60 free delivery HK

12/24V to 5V/5A - Shenzhen free delivery SMPS care

Two of these internal UK GBP 16 each :-(