If it’s a clone as many are, then any gen 3 slide will fit. The switch is a really simple device, just a wedge that moves the transfer bar to reset the sear and then releases it. It attaches to the back of the slide on the little part that holds the striker spring. Since it was patented, you can look up how to make one. Not hard, but a felony to have one.
i am not a Glock fan, but did build a p80 to see how the Glock worked. Actually a lot of nice engineering went into it. Simple design, but works well. It has several safeties, the sear can’t drop until the trigger moves back. Also a striker block that’s activated by the trigger, so it’s drop safe. The reason the trigger is not crisp like a single action is the striker is held only partially compressed until the trigger is pulled. The take up in the trigger moves the striker to the fully compressed position and then the transfer bar/sear moves down, releasing the striker. Very few parts. The magazine catch spring is simply a short rod that slips into the right spot, all molded in to the frame.