While pondering a “ring switch” I was reminded of another low-tech solution. Two screws placed close together. Metal ring across them will complete the circuit. (Disclaimer: Low Voltage Only! Keep it under 24VDC.)
Since I’m known for over-engineering, I made a quick 3D printed version to test it out. No soldering — screws hold pre-stripped wires in place. Threw in a magnet to attach it to anything ferrous/magnet friendly, or use double-faced foam. Since the end of the cord might droop, I modeled in a plug holder to take some strain.
Not the target solution, but a good early morning thought problem.