The US government runs a court information search service known as PACER. It is basically a repository of public documents which can be searched for all types of court records. The last I knew, it does not include Supreme Court documents or Tax court records. It is a paid service used by anyone from lawyers to ordinary citizens to journalists. It was implemented about 15 years ago and has had a reputation for being a bit “glitchy” and not keeping up with the times, at least as far as design and functionality. This may have changed by now, I honestly don’t know.
That being said, the fees are considerably cheaper than the more commercial services, as you are charged only for the documents which you actually download. Of course many times you will need more information to begin your search, but if you have more of the what, wheres and whens pertaining to the records you want, you can save some money going this route.
There has been a bit of controversy recently involving this Gov service and a firefox plugin called RECAP. Basically, when using the plugin, the records which are retrieved from PACER are also stored in the public domain archive created by the developers. So the next individual (using the firefox plugin) who requests the same documents can now access them for free from the public domain database. In this manner, millions of documents are being retrieved from PACER and stored for anyone to access for free. But because PACER (a government service) actually makes millions of dollars by charging for this (public) information, they are understandably not happy with the archiving and subsequent free access provided to everyone.
But the other side of the argument is that these documents are already in the public record and because anyone has the right to obtain them from the government, they should also be able to obtain them from other sources.
I am providing a link to the RECAP plugin, but I do not know what the latest developments are with this so I suggest you look into it a bit further before doing anything with it. I take no responsibility for your use of this. It is up to you to make sure there are no liability issues which could come back on you.