I don't know how it all works with them, but can you put whatever disabled type stickers that you choose on them?
I parked my car this morning, went to do my things, came back and only then noticed the sticker on the rear windscreen.
It was a small rectangle (like ones for garages/radio stations) in orange and blue which I took at a glance to be an RNLI one. It was only when I returned to the car that I realised it was a mobility one saying about needing room for wheelchair access
I was parked too close for a wheelchair to have gotten in, and there is no way that I would have done that intentionally. I have spent the day hoping that they didn't come back in the time I was gone and have to give up or anything....
So, really just a plea - put a BIG sticker on, or a big arrow pointing to the little sticker. I hate the idea that other people are going to park too close too by not noticing.