Fiber Artist Supply Co.
We use the same adjustable power supply for all of our winding equipment. It's a pretty simple unit that allows users to adjust the speed of their winder with a little knob. These have performed well in the field, but they are by no means industrial units, and we make replacement units available at a very reasonable price.
They can also be purchased on Amazon without our logo or the little wooden block with rubber feet: https://www.amazon.com/YUNBO-Adapter-Voltage-Adjustable-Transformers/dp/B07K1LV2CM?th=1