Need help with build a custom circuit for the backup battery

[RyanN]

Here is the latest schematic for the backup battery charging circuit. http://ifirobotics.com/docs/first-backup-charger.pdf

As I understood the rules, you could either build this already configured circuit, or you could make your own that served as the same purpose. As we may use a camera this year, it would be great if my interpretation is correct and I could just swing by RadioShack, pick up a Variable Voltage Regulator, a potentiometer, some diodes, some resistors, and put it all together myself with my own wiring method.