Supporting Docs - Nimbus/Blue Badge

Hey all,

I’m looking for advice on obtaining supporting documentation for blue badge and Nimbus card applications. I have a hidden physical disability that’s also dynamic and varies significantly from day to day. I’ve applied for a blue badge and my council has requested further documentation. This documentation needs to include a written letter from a HCP about how my disability affects me.
I’m really struggling to get documentation. I’ve asked my hospital specialist, GP, and physio. They’ve all said they don’t write letters and to just use appointment summaries, but my council is saying it isn’t enough evidence. I’m feeling a bit stuck. Does anyone know if there’s someone else I could ask, or something specific I could say to my GP to get them to write a letter?
For reference, so far I’ve submitted my diagnosis, medication, written answers to their questions, and my medical summary from my GP (which, for some reason lists my disability as a “significant past” issue and doesn’t include my medication). Please note that I do not qualify for PIP based on my visa status so that is not an option.
Thank you :)