Have you tried the obvious sources? Bloomberg, S&P, Nasdaq. Fintech isn't a cheap game. If you get your data from small data vendor startups, you risk getting poor fundamentals data. You don't want to waste time on debugging the calculations when you could be iterating. Some brokers like IB are also have a data vendoring side business.

If you are really tight on cash, try Intrinio. No idea about their quality but they have been around for a while.