I did your search and found  the following here. Without anywhere else to share I thought readers of your Thing would be a good audience. Explains why a normal button wont do.

Question

 

What is the difference between a push button
switch for an emergency stop and a general-purpose push button switch?
 

 

Answer

A general-purpose push button switch is used for controls, e.g., to start
machine operation or to switch modes. An emergency stop push button switch
is used as a safety measure to stop hazardous parts (loads).

An Emergency Stop Switch must be highly visible in color and shape, and
must be easy to operate in emergency situations. The following
requirements are specified in the European Standard EN 418 (International
Standard: ISO13850).

1. A direct opening mechanism must be installed on the NC contact.

2. There must be a self-holding function.

3. The button must be a "mushroom" head design or something equally easy
to use.

4. The button must be red and the background must be yellow.

In addition to the 4 points mentioned above, the emergency stop control
circuit must have countermeasures for each category.

There is no difference between a general-purpose push button switch and an
emergency push button switch regarding the function of the NO contact.

A general-purpose push button switch doesn't have a direct opening
mechanism on the NC contact. If the contact welds, conduction will be
maintained and the device cannot be stopped in a hazardous situation
(load). If this occurs, the device may keep operating in the hazardous
state. Therefore, use the NC contact of an emergency stop push button
switch for safety applications.