There exist rear flashing lights with built-in camera. They cost about $100. It may be worthwhile getting one just to be able to record what is going on.
Don't make contact with the harassers. It could escalate, and then you're alone in the dark with some bad guys.
Do contact the police if you feel threatened, especially if it's been the same vehicle on more than one occasion.
Do document each incident. Even go into your past and jot down approximate information from past incidents. The more information you can provide, the more the police have to act upon.
Do look up local cycling clubs and ask for advice from them. You may find people willing to ride with you. Or you may find others who have encountered the same vehicle.
Do carry mace just in case you're put in a position where you have to defend yourself.
Don't be afraid to scream at the top of your lungs when you encounter the vehicle and its driver behaves badly. Cowards don't like to draw attention from Good Samaritans.