The short version is what you're asking for is going to be an uphill battle. Data aggregation companies don't want to disclose their sources because their services are often used by debt collectors and other organizations who want to find people who don't want to be found. If the sources were public knowledge, debtors could avoid them to escape debt collection agencies, for example.
The comprehensive list you're looking for doesn't exist. Each data aggregation company has a different list which is the result of many private agreements they have with their sources. If you want a list of the sources, you can't ask the data aggregators.
You can ask the sources themselves. Because you don't know who they are, you have to guess. Any company that puts a card in your wallet would be a good place to start. Under California Civil Code 1798.83, you can email companies and ask them to provide you with a list of all the direct marketing companies they sold your information to. Try making a request to your insurance agency.
1798.34 also allows you to ask California government agencies to provide you with an accounting of everyone they disclosed your information to. A 1798.34 request to the DMV should be a rich source of data providers.
There's also lists of companies involved in the data aggregation ecosystem in the consumer finance protection board's list of complaints:
https://data.consumerfinance.gov/dataset/Consumer-Complaints...
One surprising thing I found out during the talk is that pizza chains are a rich source of data for these companies. If you think about it, this makes perfect sense. The data includes a guaranteed link between a person, a place, payment information, and a phone number.
> when a court needs to order that someone's information be purged
I don't think this is a thing. A friend had to deal with a DV case and I got to see how all the legal machinery involved works. The court doesn't even bother trying to purge the victim's data when they move out and try to stay away from the abuser. The court simply moved the victim and the DV support organization told them to stay off social media and not to give the new address to anyone (including pizza places.)
That being said, the federal government does have a comprehensive list of all the agencies which are members of the federal privacy council. In theory, these agencies are supposed to have a data integrity board which provides oversight for any data they keep on Americans.