Button Cover for Part 103 Without Full PCB Assembly
Unfortunately most appliance repair parts are assemblies, especially when you get into control panels.

Partially because its hard to inventory and sell the hundred pieces that make up just the buttons on your microwave vs just selling the entire section to replace.

Also because its faster to replace the whole assembly.  Its made to be taken out and replaced.  The individual pieces of it were not.  For the DIY people who don't mind spending an hour carefully prying plastic clips apart and replacing the button, the smaller parts would be nice.  But for the repair guy who just wants to get it done fast and move on to the next job, replacing the whole panel makes sense.

Besides, if that button broke, odds are there are others that have seen the same strain over the years and are close to failing too.