I did exactly that on one of my vehicles. In my case, there was +12 available when the lights were on and ground available through the door switch when the door was open.
There were diodes in the car.
So, all it took was a buzzer between the (switched +12) a diode connected to the door switch. The isolaiton was already present, so it only worked with the driver's door. The diode is effectively a (wired OR) gate.
If the isolation isn't present, then you have to add another diode to the door switch.
The buzzer I used had to be replaced periodically because it didn't hold up over the temperature extremes and 17 years.