The pushbutton switch behind the trigger has recently gone from intermittent to nonfunctional, but everything else still works fine: some simple surgery should suffice…
The handle has a flip-down cover, for the battery compartment and °C/°F switch, that pivots on molded hinges. The cover’s hinge pins are rectangular with a slight bevel and the case sockets have a notch that will just clear a properly aligned pin. Given this hint, you’ll get the cover off much faster than I did:
Remove the obvious screw and press the latches while prying the two halves apart. A small screwdriver helps persuade the latches to release their death grip:
The parts heap didn’t have any suitable through-hole pushbutton switches, but I managed to solder an SMD switch in place; the original switch is parked atop the IC for reference. Yes, the white button is slightly taller than the original black one, but it doesn’t matter:
Then it’s just a matter of tucking everything in place:
There. That was easy.