As much as I truly love replaceable cords, I'd be more than happy enough if I could just unscrew the shell of the device, unscrew the power wires from where they attach, and put in any cord. Where I care about waterproofing, some silicone caulk is an extremely cheap (and removable) fix.

Unfortunately practically everything you can buy now is welded plastic halves, or easily-broken clips. So even when you might be able to do this internally, you have a high chance of breaking the shell even if you know what you're doing.

This is such a terrible idea for sump pumps!