12V - 0,67 A USB Wall Charger for iPod Classic
There is no USB charger other than USB-C that will supply more than 5V DC. 

USB-C (3.1 spec) provides for power delivery and will negotiate up to 20 V. However, the iPod Classic is not USB 3.1 compliant, so it will not negotiate with those chargers.  

You need the original Apple charger designed for that device.