Small current circuit breaker

I had an Arduino Nano fail due to over-voltage when I used a breadboard power supply to power my breadboard. The breadboard power supply used an AMS1117 linear regulator to reduce the 12V from the plug pack I was using, to provide the 5V needed by the Arduino and some other modules. The AMS1117 failed (presumably due to overheating) and let almost the full voltage from the power supply through to the Nano and other modules. Fortunately the other modules survived. However I decided that I needed some protection against this happening again. I tried a fuse and a 5.1V zener diode, which worked quite well but after accidentally blowing the fuse twice I realised that I needed a resettable circuit breaker, not a fuse. I looked on the internet for a suitable circuit breaker, but the lowest current rating I could find was 1.5 Amps, much too high for my requirements. So I decided to build something to do the job.”