Cut-Off connector on Mighty-board ??

I don't know anything about a mighty-board, just going off my personal electronics experience here.

But, it doesn't really matter if a switch is normally open or normally closed when connected to a IC or computer board. This is because the computer reads the switch and determines a pre-programmed action based on the position of the switch. If it's a normally open switch, the programming tells it to continue normal operation unless the switch is closed, and vice versa.

The way the circuit works is that as long as the external switch is in normal state (closed) 5 volts will flow through the circuit and it keeps the extruder heaters working. However in the event of over heating the external switch will open and the 5v will no longer be there so the MCU will shut down the FET on  troubled heater via EX1-HEAT pin or the EX2-HEAT pin. These won't work on the power supply since the power supply is not controlled by the MCU.

For the power supply you would need a relay controlled by 24 volts. Put a thermal switch across the 24 volts and have the line side of the AC power from the power switch go through the relay contacts on the N.O. side. So when the circuit is energized and 24 volts flows through the thermal switch it will energize the relay switching it from N.O. to closed and thus supplying power. If the thermal switch opens it will cause the relay to de-energize and return to N.O. position which will kill power to the supply.

I ninja edited my post and added an alternate course of action for you.

Is your power supply getting that hot? I have checked mine right after a 30 minute print and it was cool to the touch. It's built in fan does a good job at cooling.

Anyone know of a good place to purchase some of these connectors ?
I'm not sure what to call them, so my searches have been negative.
(need the female part with screw-terminals)