For really fast action, the PSX-AC Circuit Breaker modules are probably the king. THe Airpax Snapak Magnetic Circuit Breakers are very good, but I can't seem to find the fast acting ones without the hydraulic delay anywhere, those are the model you'd like to have.
Here's the Sensata-Airpax Breaker Datasheet, so tantalizing close, yet seemingly unavailable. You used to be able to get the instant trip models from Digikey, but now they only stock the slow ones.