We have an ancient Saisho MW4500 microwave oven that has a keypad by
which any cooking time may be input.

Looking around you now seem to get either a rotary dial or three timer
buttons, but a limit of 10s steps in the timer.

Do any microwave ovens still have a keypad and a 1s cooking timer?

We've seem a Panasonic which has 10min/1min/10s/1s buttons, but
pressing so many would be a real pain....and no, my wife will not
round up/down to the nearest 10s interval which is the obvious thing
to do.