I just finished replacing the first of many stop buttons on my Crytopay swipers. They are from E-Switch ordered through DigiKey Electronics online. Part #EG5712-ND. It has the same look and feel of the 'old' original buttons that are flat. This new button fits right in the opening with no modification needed to the plastic housing. The button has the same 4 leads, two for the LED and two for the voltage drop. First picture is one with the new button installed. Tested it out, works just like new at a 96% savings over purchasing a brand new swiper.
The second picture is the back of the swiper with the metal face-plate removed. There are 4 oval shaped holes in the upper left corner that need to be connected to the new button. 24 gauge wire soldered to each lead on the button, then to the corresponding oval hole. If you are looking at the picture, the top oval hole #1 is the - lead to the button (the one lead off the back of the button is marked with a - sign). The oval hole at the bottom of the four, #4 is the + lead to the button (this one is also marked on the back of the button). The other two oval holes that are at 45 degree slant are the NO (normally open) connections. There would now be just two leads left on the back of the button. One lead from the back of the button would go to the #2 oval hole that is at a 45 degree angle, the other lead from the back of the button would go the #3 oval hole that is at a 45 degree angle.
If you have, like I do, the very old first swipers, the original button is soldered directly to the circuit board. Once you take the metal face plate off, you have to gentle heat up each lead that you will see sticking through the oval holes to remove the bad button without damaging the circuit board itself.