Renting/Hiring a car with a driver


Normally, I am all about trains, buses and other public transport (or if necessary renting a car and driving by myself) but am facing that it is difficult to actually reach the Val d'Orcia area without spending half the day in a train or needing to change 4 times.

I am thinking about renting a car, but don't thik I am willing to drive inside of Florence (where I live). I read several times that it is possible to hire a driver with a car, but have no idea on where to look for that. Any suggestions? Maybe even recommendations for a driver or a rental company?