Does anyone know of a resource that lists late fee maximums for consumer loans (specifically auto) that covers each state?

A free resource? This might be your best bet, but it is 6 years old, but it does give the State law citations that would allow you to check to see if they have changed.

https://www.docutech.com/wp-content/uploads/2012/12/Late-Fee-Table-2012.pdf

I saw that one but noticed that it doesn't always cover all late fee provisions. For example, in California they only list real estate late fees. It was the best (free) thing that I could find too.

We might be willing to pay for one, it doesn't necessarily have to be free.