Another answer is to find a higher voltage supply and mate it with a cheap power supply module. We’ve also seen non-PC power supplies put in a PC case.

TK discusses a portable power supply module known as a Battery Shield for Raspberry Pi and Arduino.

The power supplies have overvoltage and overcurrent protection and an LED indicator. For ease of installation, each model can be mounted on a standard DIN rail. L-com’s new open-source Arduino PLCs ...

One of the boards of the power supply module rectifies the incoming line voltage to a high DC voltage (about 400 volts). The second board then does DC to DC conversion to the desired output.