That's awful and shameful that no firm would take the case. I was helped by a reporter friend that published my narrative of what happened to me, which got the word out to a lot more firms. Eventually I was contacted by several, and eventually settled on one that was focused on pursuing cases similar to mine.
I guess my two cents would be to not get down and assume no one will help. I was furious about my experience, it really shocked me on a fundamental "I don't trust the system anymore" level. I was pretty close to just becoming more cynical and just deducing to hate all cops forever. I even had some friends say "well you must have done something" to deserves it. It was a terrible blow to hear that.
But I fortunately was so upset I didn't want to just get angrier, I wanted justice. I wrote my experience down while it was still raw, and shared it with some friends, one of whom was a reporter. I really did this initially for validation, I wanted someone to know what happened to me, to agree with me that what happened to me was an injustice: because up to that point I felt like no one cared. And I wanted to do something. I had to do something. I wasn't going to just accept what had happened to me as inevitable and just part of the system. It was wrong, horribly wrong.
My reporter friend asked if he could publish it, I was frankly surprised he wanted to publish it verbatim but I guess a raw emotional narrative makes better copy than and interview. And from that I started getting emails from law firms.
I know how awful it can be to unjustly treated by the police, how helpless you are, how dehumanized you can be, how violated the experience can be when you did nothing wrong. Don't give in. Youre not alone. You're a survivor. Yes, It can be hard to fight back, but it's worth it. It's a positive experience for me now, because you realize you can help prevent this from happening to someone else. That you can get justice. That you're not crazy, that what happened to you was wrong.
Just know the process is long, and there will be set backs. The system is overloaded with cases, don't expect anyone to hand victory to you quickly or easily. The cops will close ranks, and lie for each other. The courts will let them, just keep at it. Eventually they'll either settle to make you go away to spare them the continuing costs, or you'll get your day in court.