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.

I used Sugru, which you can buy on Amazon or Target and made my own gasket. The object is to not make it so thick just about a string of 1/4 inch Surgru around the inside, screw the bottle in just enough to make a slight screw impression and then take the bottle out and let it dry for 8-10 hours. You've now made your own gasket with a rubber material that will last a couple of years.