need a new carbonating button

There are many used machines on Facebook marketplace or Craigslist that you can find and buy and then use them for repair. I for one found that the button depresses too much and it sounds like that is happening to you, hence the breakage. I took some popsicle sticks, cust them to make an inch length, glued them together, and glued them between the button and the housing. Then I didn't need to press so hard to get the carbonation out of the can and into the bottle. Hope that helps for any future endeavors.