I've just a quick ebay search, and something like this kit would get you up and running, provided you can figure out the existing power supply, and get it working for the steppers - CNC Router DIY Kit 5 Axis Breakout Board +3x M542 Stepper Motor Driver 1.0A-4.5A | eBay

If you scroll down the page, it has some pretty simple but clear wiring diagrams, which should help clarify what's needed, and how they connect.