I was at Hannays yesterday, got a Johnson ultima auto bilge pump sw out of the bargain bin for $5.
Of corse it did not work :/, so I carefully cut it apart and found the FET that turns the motor on was... Blown open
So I found one I had, that had similar specs (the original one was rated at over 100A and had a vary low "no resistance") but I figured I could get buy with a smaller one as my pump only draws 3A. Soldered it in kinda upside down.
Put a small heat sink on it and glued it in place with 6200 RTV.
Tomorrow when the RTV is cured I will test again, then "solvent weld" the case back together.
And yes... I do understand it would have been easier to just buy the new one for $40