Inverting the logic of the inhibit pin on TI PTR08100W
I think your assessment that there are fewer N.C. type switches is somewhat short sighted. It is true that most TACT type switches are indeed N.O. type but many other switch types offer Form C type contact arrangements that offer both N.C. and N.O. on the same part. 

If the input voltage on your regulator is always present you can leverage that to your advantage with some simple additional circuitry to provide the inversion logic that you require for use of a N.O. type switch. Here is how to connect it up. 

Use an NPN transistor with its emitter connected to GND. Tie the collector to the inhibit pin on the regulator chip. Then connect a resistor from the base of the NPN to the input voltage supply rail. A 10K resistor may be a suitable value. Finally connect the N.O. tact switch between the base and GND. A small signal type transistor such as a 2N3904 is probably the best type to use. 

Pressing the switch turns off the NPN which in turn frees the GND connection at the inhibit input.