Someone suggested a 555-based timer, and that's the way I would go as well. Google "555 timer" and there will be plenty of sample circuits - just a half-dozen or so components, bit of Veroboard, and you can probably do it for a fiver. Like this one? I built one of these a while ago when my wife gave me three days - over a weekend - to build a slow-speed turntable to display a piece of work. All I had to hand was a spare stepper from my 3D printer and the matching Pololu driver. All you need to do is generate 5V pulses so run the circuit off any convenient source of 5V; direction can be switched, and enable hard-wired. Timing isn't an issue as long as you get the pulse length above the minimum for the driver.