Am leaning more toward a charger used to charge up batteries ala automobile. Mine is quite small and could easily have been put in carry on luggage back then.
If the victem is given enough charge to produce unconsciousness I doubt if they'd remember it. Remember the first wife (just) assumed she had been drugged as an explanation of why she was out for two days.
I'm not buying that it would wipe out enough memory far enough back. She wouldn't remember him fooling with his apparatus? Risky, very risky.
Occam's Razor and all that. Slipping someone drugs in food or drink is simple and easy. They just remember going to sleep.
And we already have the presence of the unexplained pineapple in which an unknown and untested for drug could have been delivered.