Is there any organization in the US that help with the financial cost of an MRI?
I don't know much about places that would help other then, say, a free clinic. I know in my town there's a great clinic run by practitioners of all kinds where those without insurance can seek treatment for just about everything from psychiatry to podiatry and all points between. There may be an opportunity to negotiate rates with your local hospital. I'm at the far reaches of my knowledge here so perhaps someone with more medical or insurance expertise will chime in.
In the meantime, I hope that you're doing OK and finding ways to relief some relief from your symptoms. Cheers!