where to buy a magnetic breaker?
You won’t buy em for your electrical panel... Only T-M, Thermal-Magnetic, breakers are available. The Thermal protection unit of the breaker is for overload protection of the branch circuit wiring. The magnetic unit provides short circuit protection. It usually trips the breaker open in a matter of milliseconds. An electrical short circuit can cause a dangerous electrical explosion if not cleared quickly...
The only place I can think of where a Magnetic circuit breaker is used is on a piece of equipment. It is never used to protect branch circuit or feeder wiring...
Per NEC, UL, NEMA, only the manufacture’s breaker type/stye can be used in an electrical panel. A label on the back side of the electrical panel’s breaker cover door lists the manufacture’s type/style(s) for the breaker(s) that can be used in the panel. Using the wrong breaker will void the UL Listing.
Here is a video of the inside of a circuit breaker and how it works. Note the circuit breaker that is used for the demonstration is a EATON type/style BR breaker, not a Square D QO circuit breaker. A Square D QO breaker works on the same principal but in my opinion is of a better build quality.
The guy making the video does a pretty good job except, imo, when it comes to his personal electrical safety.