Getting insurance can be done online in about 5 minutes and the registration at the DMV equivalent is your problem (as the buyer) afterwards and can be done anytime in the next 2 weeks.
I can see that happening for second-hand cars but not for new cars that have to be issued new plates. But maybe things work differently in other countries. “Europe” is not really one place.
I got that kind of temporary plates once... at the DMV. It was quick, but they didn’t materialize magically when I needed them. Maybe it’s easier now, though.