Almost everybody on HaD (and in the Maker scene) needs power supplies, and Chinese suppliers are happy to supply as many as you like. Programmable power supplies are also available but they come at a much higher price, with very limited programming features, or in the form of "hardware + C-compiler".
This project uses Forth as a programming environment for the power supply. Using Forth as a scripting language is easy, and it leads to surprisingly simple and powerful solutions.
The entry ticket is cheap: the price for the XH-M188 linear power regulator is about $4.75 (including shipping). You'll also need a STM8/STM32 programmer ($2), and "TTL" serial interface ($0.60).
The Low-Cost Programmable Power Supply is a similar project (warning: more soldering required :-) ).