If you would like to build your very own benchtop power supply you might be interested in a DIY tutorial for Supplino. A versatile compact Arduino power supply capable of providing from 4 to 40 ...

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

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.